Constructive Solid-Geometry Methods (CSG):

Constructive models represent a solid as a combination of primitive solids. This modeling technique combines the volumes take placed by overlapping 3D shapes by using set boolean operations.

It creates a new volume applying the intersection, union or difference operation to two volumes A and B. See Figure which is self-explanatory.

The method of Constructive Solid Geometry arose through the observation that several industrial components derive from combinations of many simple geometric shapes such like spheres, cylinders, cones and rectangular solids.