OpenSCAD is a software for creating solid 3D CAD objects.
Unlike most free software for creating 3D models (such as the famous
application Blender) it does not focus on the artistic aspects of 3D
modeling but instead on the CAD aspects. Thus it might be the application
you are looking for when you are planning to create 3D models of machine
parts but pretty sure is not what you are looking for when you are more
interested in creating computer-animated movies.