Trusted teacher: CAD allows creating pieces or parts and put them together to conceive machines, ships, buildings and anything imaginable. Creating a 3D model is the first step to 3D printing, CNC machining and fabrication in general. Also it is necessary to do simulations or calculations using a myriad of techniques. FreeCAD is a free and open source software that follows the parametric design paradigm. That conception in design is the same in many other CAD software, like, for example, CATIA, Roadworks, Solid Edge, Inventor and Fusion360, just to mention some of them. This means that once we have acquire a good basis in creating pieces and assemblies in FreeCAD, adapt to any other of the former mentioned would take a bunch of hours.