Here are the best free CAD software tools (2D/3D CAD programs) for beginners, intermediates, and advanced users.
Do you need free CAD software? But you’re not sure quite what you need? Here you can learn the basic terms to make a smart choice. Also, we have compiled a comprehensive list of the best free CAD software.
CAD software is an important tool for professional architects, engineers, animators, and graphic designers. With the proliferation of Open Source projects, free CAD software is in many cases no less sophisticated than its commercial counterparts. But given the many differences between the CAD programs, it can be difficult to choose the right one.
All3DP is here to help. First, learn about the basic terms of computer-aided design. Second, you can search and browse our list of the best free CAD software.
|3D Builder||Beginner||Windows, Windows Mobile, Xbox One, and Windows Hololense||3D||3mf, obj, ply, vrml, STL|
|3D Slash||Beginner||Windows, Mac, Linux, Raspberry Pi or Browser||3D CAD||3dslash, obj, stl|
|Autodesk 123D Design||Beginner||Windows, Mac and Linux||3D CAD||123x, step, stl, x3d, vrml|
|LibreCAD||Beginner||Windows, Mac and Linux||2D CAD||dxf, dwg|
|MagicaVoxel||Beginner||Windows, Mac||3D||2d, iso, mc, obj, ply, qb slab, vox, xraw|
|SculptGL||Beginner||Browser||3D CAD||obj, ply, sql, stl|
|TinkerCAD||Beginner||Browser||3D CAD||123dx, 3ds, c4d, mb, obj, svg, stl|
|Wings 3D||Beginner||Windows, Mac and Linux||2D/3D CAD||3ds, fbx, obj, dae, lwo, wrl, rwx, stl, wrl, x, xml|
|BabaCad||Intermediate||Windows, Mac||2D CAD||dxf, dwg|
|Design 3D SE||Intermendiate||Windows, Mac||3D||dae, eps, psd, STL, 3ds, dxf, obj, vrml|
|DraftSight||Intermediate||Windows, Mac and Linux||2D CAD||dxf, dwg|
|eMachineShop||Intermediate||Windows||2D/3D||igs, sldprt, stp, iges, 3D dwg, STL|
|FreeCAD||Intermediate||Windows, Mac and Linux||2D/3D CAD||step, iges, obj, stl, dxf, svg, dae, ifc, off, nastran, vrml, Fcstd|
|HeeksCAD||Intermediate||Windows, Mac and Linux||3D CAD||dxf, heeks, iges, stl, stp, svg|
|Meshmixer||Intermediate||Windows, Mac and Linux||3D CAD||amf, mix, obj, off, stl|
|QCAD||Intermediate||Windows, Mac and Linux||2D CAD||dwg, dxf, dwf, pdf, svg|
|Sculptris||Intermediate||Windows, Mac||3D CAD||obj, goz|
|SketchUp||Intermediate||Windows, Mac||3D CAD||dwg, dxf, 3ds, dae, dem, def, ifc, kmz, stl|
|SolveSpace||Intermediate||Windows, Mac and Linux||2D/3D CAD||dxf, eps, pdf, svg, hpgl, obj, step, stl|
|Autodesk Fusion 360||Advanced||Windows, Mac||3D CAD||catpart, dwg, dxf, f3d, igs, obj, pdf, sat, sldprt, stl, stp|
|Blender||Advanced||Windows, Mac and Linux||2D/3D CAD||3ds, dae, fbx, dxf, obj, x, lwo, svg, ply, stl, vrml, vrml97, x3d|
|BRL-CAD||Advanced||Windows, Mac and Linux||2D/3D CAD||dxf, iges, stl vrml, x3d|
|DesignSpark||Advanced||Windows||2D/3D CAD||rsdoc, dxf, ecad, idf, idb, emn, obj, skp, stl, iges, step|
|nanoCAD||Advanced||Windows||2D CAD||sat, step, igs, iges, sldprt, stl, 3dm, dae, dfx, dwg, dwt, pdf, x_t, x_b, xxm_txt, ssm_bin|
|OnShape||Advanced||Windows, Mac, Linux and Browser||2D/3D CAD||sat, step, igs, iges, sldprt, stl, 3dm, dae, dfx, dwg, dwt, pdf, x_t, x_b, xxm_txt, ssm_bin|
|OpenSCAD||Advanced||Windows, Mac and Linux||3D CAD||dxf, off, st|
3D Builder is a dedicated app for 3D modeling and printing that is available for desktop PCs and other Microsoft platforms (Windows Mobile, Xbox One, and Windows Hololense). Similar to Autodesk’s Gallery, users can download the 3D models created by others to modify and 3D print them.
Using the touchscreen interface with gestures, editing and tweaking 3D files is quite an immersive experience. The integration into the Windows phone has another perk: The mobile app also enables the user to scan objects and convert them into 3D files using the device’s camera. Simply take a series of photos of the object from several angles, and images are stitched together to recreate the object as a 3D model.
3D Slash is not your run of the mill CAD software since conventional features like extrusion, revolution or sweeps are not part of the CAD program. Instead, it is centered around the cuboid, a solid block that can be subdivided into smaller blocks of identical size. Just think of Minecraft, and you’ll get the idea. Users create their 3D designs by working the cuboid with an array of tools that will not be familiar with most other 3D modeling software: hammer, trowel, chisel, pulpwood, and drill. Thus, you use the hammer tool to remove individual cubes, while the trowel adds cubes and so forth.
3D designing with these tools is easy, even for beginners. With only a little training you can achieve impressive results, like a light saber (see our tutorial below). Also, you can import, and modify existing 3D designs. For your convenience, this free CAD software ties in with a range of online printing services, and model repositories. Or you can simply export your 3D design to STL, and print it on your 3D desktop printer.
The playful, hands-on approach will be especially gratifying for hobbyists who occasionally want to create their 3D designs without having to master the mysterious lore of conventional free CAD software.
Autodesk 123D Design is a free CAD software created by Autodesk. It is similar in scope to SketchUp, and inspired by Autodesk’s Inventor. It is a powerful, yet relatively simple to use 3D creation and editing tool that can work seamlessly with most 3D printer models in the market.
123D Design features a simple and intuitive graphical user interface. Meshes are designed by placing primitive shapes in the design area. These shape’s properties can be refined with an array of tools, including more advanced techniques like sweep, and loft. As well as the more basic drawing, and modeling capabilities, it also has assembly and constraint support. There is also a library of premade blocks, and objects, which can be valuable timesavers. Also, the capability of importing SVG files makes 123D Design a handy 3D modeling software tool to create mechanical parts from drawings stored in that format.
Our verdict, one of the best free CAD software for beginners who want to get a solid foundation.
UPDATE: As of spring 2017, Autodesk has discontinued its popular 123D software line of free 3D modeling and scanning tools. However, the CAD programs are still running on many computers worldwide. For this reason, All3DP will keep its tutorials and reviews accessible for as long as these CAD programs can be run.
LibreCAD is an open source free CAD software. It contains basic tools you will need to model and modify your designs. Since LibreCAD displays only 2D views, it has a slim file size of only 30 MB. But not to worry, it can display isometric views. Though the free CAD program satisfies common drawing needs, the functionality will not overwhelm you, unlike other free CAD software. LibreCAD’s UI is uncluttered, and overall the CAD program is suitable for beginners.
MagicaVoxel is an easy to use, free CAD software that is reminiscent of Minecraft. The smallest unit within the program is the eponymous voxel, a block that is used to create stunningly sophisticated designs.
Users will easily find their way around the clearly arranged user interface. To the left, are rows of color palettes used to paint voxels in the absence of traditional textures. Palettes can be customly defined or loaded into the program. Next to it, a small range of render settings ensures quite memorable results. The viewport is found at the center. To ease the 3D modeling workflow, brushes and patterns consist of voxels are predefined.
Working with the tools in MagicaVoxel takes some getting used to, as you choose between modes that affect only the surface of a mesh, select layers or penetrate the volume of a mesh. The consequences of these techniques are as far reaching as many sophisticated tools in traditional 3D modeling programs. As users who have taken to them no longer depend on assembling complex designs voxel by voxel, but can sketch them out quickly and efficiently.
With games like Monument Valley and Minecraft voxel designs have become very popular. Free CAD software like MagicaVoxel is a brilliant choice for creating 3D voxel art for use in games or illustrations.
An alternative approach to traditional 3D modeling is 3D sculpting. Whereas some commercial options on the market have pretty steep learning curves, SculptGL will go easy on you. It includes only the basic tools necessary and allows you to give you a sense of the sculpting workflow. What is more, you can have all that in the comfort of your web browser.
As in more advanced sculpting tools, the main concept is that you don’t try to create a high-resolution mesh right from the start. Instead, you build up levels of details step by step. The groundwork is always to define the silhouette (arms, heads, limbs) in very broad brushes. From there you can switch to smaller brushes, and sculpt large details, pronounced muscles, fingers, and the like. Only then should you add intricate details like wrinkles or scars using finer brushes.
This being a free CAD software, the number, and complexity of objects are limited to the minimum. For anyone just curious about 3D sculpting, SculptGL is a great opportunity. If you want to level up, you should give Sculptris a try.
TinkerCAD is a free 3D CAD program, now owned by Autodesk. Using basic modeling operations, TinkerCAD allows you to join these primitive shapes complex objects. But there is more to TinkerCAD, the functionality extends to joining, and subtracting shapes. After mastering these basic techniques, even newbies to CAD software can produce impressive results like Raspberry Pi cases in no time.
If you are looking for a tool to get your feet wet, you will love TinkerCAD’s intuitive approach to common concepts, and tools in free CAD software. It also can be used for laser cutting.
Written in Erlang, Wings 3D major strength lies in its advanced subdivision. The intuitive user interface will make anyone a 3D modeler in no time. In addition to standard tools like move, scale, extrude etc., the free CAD software features advanced tools such as sweep, plane cut, bend, shear, and inset. The other big selling point is its AutoUV facility, that allows you to export an unfolded image of your model’s surface for painting and texturing.
Wings 3D’s range of features is exactly right for beginners who don’t want to get overwhelmed, and yet get a thorough foundation in 3D modeling.
Antimony is the sort of free CAD software you should give a try, in case you are in need of a fresh perspective on parametric 3D modeling. It’s basically the love-child of a 3D designer and a programmer.
In this program, every mesh is broken down into the smallest logical components, primitive shapes and transformations (boolean and other) that allow you to generate complex objects by joining or subtracting them. Unlike other similar programs like OpenSCAD, that tend to frighten away beginners with long code documents, Antimony’s workflow is much more intuitive. The user connects nodes that define shapes and transformations in graphs.
The nifty modeling workflow is suitable for most seasoned designers. In case the built-in shapes don’t cover all your needs, it is possible to define custom shapes. However, this is not down everybody’s alley, as Antimony represents shapes with a prefix string syntax. This free CAD software was conceived of and is maintained by Matt Keeter, an engineer with the 3D printer manufacturer Formlabs.
Take note that as of summer 2017, this free CAD software was in beta mode and is not recommended for critical work. We look forward to seeing major software publishers picking up the innovative ideas of Antimony in their products.
BabaCAD is another interesting free CAD software with some truly amazing features. The program runs fast, even on older computers. But more importantly, the UI is very user-friendly, designers are treated to a clearly structured menusystem that allows finding the many advanced tools swiftly. More advanced users can take advantage of the command window to quickly enter and modify properties and commands of their 3D models. In many respects, this CAD program is almost on par with commercial alternatives. As it includes useful features like organizing and grouping objects in layers and blocks. Drawings can be dimensioned in a breeze with smart quick dimensioning. Also, object snap is an indispensable tool for assembling complex drawings.
Beyound any doubt, the most fascinating feature of BabaCAD is its LISP compatibility. LISP scripts enable users to create extensions of the program to their needs and exchange. For decades a unique selling point of AutoCAD, BabaCAD became the first free CAD software to implement this feature. Many of these scripts are available for free online. In conclusion, even ambitious CAD designers are bound to find BabaCAD’s LISP compatibility useful.
StrataSys has made its name manufacturing industrial grade 3D printers. It was only a matter of time until the company decided to expand into 3D modeling and CAD software. But Strata Design 3D SE is capable of more than designing models for 3D printing. StrataSys confidently aims at architectural visualization, virtual reality and other profitable applications. This CAD software wants to take the sting out of learning a new tool by overtly basing its UI on Adobe’s user experience. Add to this a comprehensive feature set and you have the formula to a promising CAD tool.
As your 3D CAD abilities mature over time, you can take a gander at Design 3D SE’s commercial big brother. It brings you an extended feature set in lighting, publication of AR/VR-content, animation and many more modeling tools.
DraftSight is a free CAD software from Dassault Systèmes, the publisher of industry giants such as CATIA, and Solidworks. Thanks to its clear user interface, anyone can learn the program quickly. DraftSight has all the necessary tools to create 2D technical drawings. The elements of designs are stored in layers, enabling accurate revisions. Designs can be exported to PDF for use as construction sheets.
Dassault Systèmes offers support for users of the free CAD software. Among many other features, the professional version of DraftSight can compare designs, and display the differences, append PDFs to the project file, and add standard hardware symbols to your design.
eMachineShop is a free 2D/3D CAD software. The program is published by an online CNC milling and printing service. That’s why you can order parts directly from within it. This software is comprehensive enough for advanced designers and simple enough for beginners. In terms of drawing, eMachineShop brings all the standard features you could expect from a CAD suite, like chamfering or sheet metal bending.
However, in case you have no prior experience, use one the handy design wizards to design flywheels, heatsinks, hex nuts, front panels and more pre-drawn parts. But eMachineShop can do even more for you. The program continuously analyzes your design and alerts you to impractical design features, non-manufacturable parts and high material cost.
FreeCAD is a parametric solid free CAD software. It is made primarily to 3D design real-life objects of any size. Its parametric modeling capability allows you to easily modify your 3D design by going back into your model history and changing its dimensions.
Being an open source software, its feature set is oriented towards the community. So be prepared that FreeCAD can be a bit overwhelming at first. But if you make an effort to dig deeper into the free CAD software, you will be rewarded with an awesome set of features.
This free CAD software offers a modular architecture that allows plugins to be mounted to the core application. It also offers a Sketcher with constraint-solver, allowing you to sketch 2D shapes; a robot simulation to study robot movements, and a Path module dedicated to mechanical machining like milling (CAM), and can output, display, and adjust G code.
HeeksCAD is a powerful solid modeling program built on top of OpenCASCADE. Among the usual editing tools are multiple ways to extrude, and a chamfering tool. Like many other free CAD software, this one takes its cues from AutoCAD, so switching should not be a problem.
But this is not all. HeeksCAD is a modular free CAD software that can be extended by installing additional plugins. So far, plugins are available for Python scripting, CNC milling, and freeform surface modeling. The later effectively transforms this free CAD software into a 3D modeler. With its active developer community, we expect more exciting features to come to HeeksCAD shortly!
The self-described “Swiss Army Knife” for 3D meshes is Meshmixer has a clear emphasis on the mechanical functionality of 3D designs. Meshmixer is designed to prepare meshes for 3D printing. For instance, Meshmixer is used to model solid prosthetics with mechanical parts. Moreover, this 3D modeling software provides some pretty sophisticated optimization techniques usually found in industrial grade programs: You can slim down unwanted mass from a 3D design, and thereby reduce the cost of printing significantly. It also allows you to automatically generate joints connecting different parts into one single device.
Also, this free CAD software has repair capabilities like hollowing, scaling, and mesh simplification making it invaluable for 3D printing.
This rich feature set makes Meshmixer a tool for advanced users, but if you are looking for one of the best free CAD software tools that seamlessly blends into the Autodesk product family, look no further.
QCAD is an old school 2D free CAD software, that is partly inspired by AutoCAD. So it is mostly geared towards technical drawing. As the user interface is remarkably neat, and clean, even beginners will find their way around this free CAD software quickly.
The modeling tools include NURBS, and Polylines. For more intricate work, you can switch into an isometric view. Also, the QCAD Library browser brings you more than 5000 CAD parts available as free add-ons (e.g. screws, nuts). Though the free CAD software is released under Open Source license, AutoCAD DWG export is only available as a commercial plugin.
Sculptris is a free 3D sculpting program by the same developers as ZBrush. It has similar, though fewer features than ZBrush. Even beginners can grasp the basic techniques of Sculptris quickly, and produce printable models.
As in more advanced sculpting tools, the main concept of this free CAD software is that you don’t try to create a high-resolution mesh right from the start. Instead, you build up levels of details step by step. The groundwork is always to define the silhouette (arms, heads, limbs) in very broad brushes. From there you can switch to smaller brushes, and sculpt large details, pronounced muscles, fingers, and the like. Only then should you add intricate details like wrinkles or scars using finer brushes.
If you want to get your feet wet in 3D sculpting, Sculptris is a great free CAD software option. For more ambitious sculpting projects take a look at ZBrush or Mudbox.
What strikes first-time users of SketchUp at once is the neat, and tidy interface. There are not many buttons that can boggle beginners trying to understand the 3D modeling software. Thanks to the intuitive tools that allow navigating, and sculpting accurately in the 3D view, it is possible to create simple 3D printable models from scratch within the first few hours of learning.
Which is not say that SketchUp is only capable of simple 3D modeling. Since SketchUp encourages users, and third party companies to contribute extensions – many of them free of charge – there is virtually no limit to its potential capabilities. The free CAD software also includes drawing layout functionality, and allows surface rendering in a variety of “styles.”
SketchUp comes with its exchange repository integrated into the program itself: 3D Warehouse – a library where approximately 2.2 million SketchUp models can be downloaded directly into the program. Also, the support of this free CAD software for 3D printing is already impressive and growing every minute.
In case you always wanted to have a go at parametric 2D/3D CAD, this free CAD software may be just for you. This capability allows you to easily modify your design by going back into your model history and change its dimensions. Also, its modeling tools include Bezier curves and NURBS surfaces. Another key feature is the simulation of planar or spatial linkages, with a pin, ball, or slide joints. This is invaluable as it will show you possible blockages, and inconsistencies in your designs early in the design process, saving you time and reducing annoyance.
3D printing hobbyists will appreciate the built-in STL repair tool that will make your 3D models printable. This free CAD software is even able to prepare 2D GCode for waterjet machines or laser cutters. The website includes a series of readable tutorials that will ease you into using the program.
Vectary is a browser based free CAD software that is currently in beta mode. Still, for its innovative UI and approach to collaboration it is definetely worth your attention.
As the API is expected to be published in the near future, the functionality can be constantly expanded using plugins. For instance, this free CAD software already includes parametric modeling. A feature that allows for quick adaptions of the mesh using sliders and selections that is mostly found in professional engineering suites like Fusion 360. But this doesn’t make Vectary an engineering program for the web, since the program doesn’t rely on precise measurements. Instead, designs are created in a 3D viewport using subdivision modeling and then transformed using various tools. Making it better equiped for the needs of designers. Also, Vectary emphasizes user collaboration as all models are saved in the cloud and can be easily shared.
Although the range of features is amazing for a 3D modeling program that runs in the browser, this comes at a price. Don’t underestimate how much memory this free CAD software takes up. Vectary’s free plan includes 5 private projects and unlimited public projects. Business options will be available soon.
Fusion 360 is a professional 3D CAD program tool by software Autodesk. Unlike other professional solid-body 3D modeling software, this program is strong in usability. Still, it covers the whole process of planning, testing and executing a 3D design. It has powerful parametric tools and analytic mesh tools that are well-suited to most challenges in industrial design. Moreover, it is able to simulate both the construction of the components designed as well as the stresses they will face once they are put to their use. Fusion 360 is also set apart by its sophisticated collaborative features. It supports cloud-based file sharing, version control and import/export of common CAD file types.
As can be expected, Fusion 360 has excellent support for 3D printing. CAD files can be directly imported into the Autodesk Printing Studio. Although a commercial program, Fusion 360 is effectively free CAD software for students and educators, as you can apply for a 3 year educational license.
Blender is a professional open-source and free CAD software for creating animated films, visual effects, art, interactive applications, video games – and 3D printed models. Blender’s dizzying array of features includes 3D modeling, UV unwrapping, texturing, raster graphics editing, rigging, and skinning, fluid, and smoke simulation, particle simulation, soft body simulation, sculpting, animating, match moving, camera tracking, rendering, video editing, and compositing. Also, this free CAD software features an integrated game engine.It is clear that such wealth of functionality comes at a price. Although Blender is free, it is by no means easy to master. Regarding modeling, it is noteworthy that 3D design software Blender includes sculpting capabilities similar to commercial options like Mudbox or ZBrush. This free CAD software provides many tools and modifiers that ease the creation of meshes intended for 3D printing – including a solution to repair meshes.
It is clear that such wealth of functionality comes at a price. Although Blender is free, it is by no means easy to master.
Blender is not suited for beginners, but if you are not turned off by a steep learning curve, and search for one of the best open-source, free CAD software, you have found it.
BRL-CAD is a free open source solid modeling program. The development of BRL-CAD began in 1979 when the US Army needed a CAD system to conduct ballistic, and electromagnetic analyses. However, this free CAD software is also suitable for academic, and industrial applications including in the design, and analysis of vehicles, mechanical parts, and architecture. You can either model in a GUI or in the command line – users of OpenSCAD will appreciate this. The brilliant modeling system of this free CAD software is based on CSG. In the past BRL-CAD was run on supercomputers like the Cray – today the program can run on a wide array of desktop operating systems.
DesignSpark is tailored to 3D modelers on a budget. In terms of functionality, the program keeps to the conventions of CAD software. This free CAD software features the usual CAD modeling tools. Also, the user interface is clearly inspired by AutoCAD. So, in case you’re looking for a free alternative to that program, it’s worth to take a closer look.
While the core features are free, additional functionality has to be bought. This concerns extended import/export options and rendering. Like some other programs, DesignSpark taps into online services. This allows you download 3D models directly into the free CAD software, and have your designs printed, and sent to you.
nanoCAD in its basic version is a free CAD software. It is another example that shows how one company did something right and inspired others to follow in its tracks: the user interface takes its cues from Autodesk’s AutoCAD. So switching from one to the other won’t be a problem.
nanoCAD supports parametric modeling, which is handy as you can revisit older designs, and adapt them to new tasks in a breeze. Moreover, it can automate a great many routine tasks. As AutoCAD, it comes with a useful spreadsheet editor. The program is uncluttered, making it suitable for hobbyists, and beginners. Still, users have a rich feature set at their disposal. The free CAD software’s functionality can be extended by various plugins. In case your projects are more demanding, you should take a look at the Plus version of nanoCAD.
Onshape is a mighty enterprise-grade CAD software suite that is free for open-source projects. It is aimed at professional level users, who want version control, and collaboration built. Onshape is delivered over the cloud as a Service. It works on pretty much every system you can imagine – even on iOS, and Android phones.
One of the most interesting features of this is free CAD software is its collaborative mode. Unlike installed CAD and PDM, Onshape gives everyone on the team instant access to the same CAD workspace and same CAD data in one central place in the cloud. Another nifty feature is the ability to manage a master design without the need to save copies or keep track of numerous different file versions.
Another approach to 3D modeling software is OpenSCAD, a free CAD software for creating solid CAD objects. It is not an interactive modeler, but rather a 3D compiler based on a textual description language.
An OpenSCAD document specifies geometric primitives, and defines how they are modified, and manipulated to render a 3D model. This allows you to create 3D designs, which are defined by configurable parameters or reuse code for other projects. OpenSCAD is centered around constructive solid geometry (CSG), and extrusion of 2D outlines.
Admittedly, OpenSCAD is not for everyone. But it’s a free CAD software for die hard modeling enthusiasts, who relish in seeing in their code come to life in the 3D printer.
The most important distinction to keep in mind is between 2D and 3D CAD software. In the olde days when designers and architects stood pen in hand at the drawing board, they designed in 2D. Early CAD software emulated this, displaying only trite top, front, and side views in 2D, and some CAD programs to this day only display 2D. Believe it or not, for functional designs many designers even prefer 2D CAD. As a rule of thumb, 2D CAD software is geared towards simple technical geometry. 2D is always an abstraction of the real thing. So, it is not an ideal tool to explore many alternatives of complex designs.
This is where 3D enters the picture. Only with the advances of GPUs, 3D rendering became a commonplace feature that enabled new tools that had been impossible on the drawing board. This allowed engineers and designers to create more complex geometries. The most radical development probably is 3D sculpting. 3D CAD software enables complex technical geometry, and designs since 3D representations are less prone to misinterpretation. Also, physical simulations are easier to implement and interpret.
As 3D modeling grew out of 2D technical drawing the line between the two is often blurry, as most CAD programs feature modeling tools from both worlds. In our list, you will find the full spectrum of free CAD software!
Many free CAD software boast solid modeling as a key feature. What’s so solid about a computer file?
Solid models supply information on physical properties like the center of gravity, volume, and mass. The idea behind the solid model is to represent a given object completely to be able to physically manufacture it. Usually, you will start with primitive shapes (cubes, spheres, etc.) which you can add to, and subtract from to model your design.
A surface model on the other hand only consists of a wireframe, and data describing the surface. These can be free-form surfaces like Bezier curves or NURBS surfaces, and others but it contains no information on the model’s content. Surface models are sufficient for many applications, like 3D animation, graphic design, and even 3D printing.
Of course, you’re not stuck with either one or the other. Most free CAD software allows you to convert between solid, and surface 3D models.