From FreeCAD Documentation
- Draw a closed 2D shape (also called sketches) on some plane in the 3D space (for example, on the ground (XY) plane, or on a face of an existing part). Sketches are a very powerful feature of FreeCAD. They can contain linear or curved segments, but also complex elements such as constraints or construction geometry.
- Extrude that shape so it forms a solid
- Use that solid either as an addition or subtraction of another solid
- Optionally, apply some finishes such as rounding on some faces