Boolean logic is all about shape relationships. Cutting holes into a geometry with another geometry or combination of different geometrical shapes to create new shapes.

SDF is short for signed distance field and describes the interior volume of an object. How thick an object is from the middle to the surface? How deep does the cylinder extend? From any point inside an object, using the SDF, it is possible to easily grab the distance to the surface of the object in order to know the depth.