A full parametric model. All FreeCAD objects are natively parametric, meaning their shape can be based on properties or even depend on other objects. All changes are recalculated on demand, and recorded by an undo/redo stack. New object types can be added easily, and can even be fully programmed in Python.
A modular architecture that allows plugin extensions (modules and workbenches) to add functionality to the core application. An extension can be as complex as a whole new application programmed in C++ or as simple as a Python script or self-recorded macro. You have complete access to almost any part of FreeCAD from the built-in Python interpreter, macros or external scripts, be it geometry creation and transformation, the 2D or 3D representation of that geometry (scenegraph) or even the FreeCAD interface.
Import/export to standard formats such as STEP, IGES, OBJ, STL, DXF, SVG, DAE, IFC or OFF, NASTRAN, VRML in addition to FreeCAD's native FCStd file format. The level of compatibility between FreeCAD and a given file format can vary, since it depends on the workbench that implements it.
A Sketcher with integrated constraint-solver, allowing you to sketch geometry-constrained 2D shapes. The constrained 2D shapes built with Sketcher may then be used as a base to build other objects throughout FreeCAD.
A technical drawing workbench with options for detail views, cross sectional views, dimensioning and others, allowing you to generate 2D views of existing 3D models. The workbench then produces ready-to-export SVG or PDF files.
A CAM Workbench dedicated to mechanical machining for Computer Aided Manufacturing (CAM). Using the CAM Workbench you may output, display and adjust the G code used to control the target machine.