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Lots of new goodies in v0.20: Release notes v0.20 - FreeCAD Documentation
(wiki.freecadweb.org)
Your own 3D parametric modeler.
FreeCAD is an open-source parametric 3D modeler made primarily to design real-life objects of any size. Parametric modeling allows you to easily modify your design by going back into your model history and changing its parameters.