Constructive Solid Geometry is the process of building solid objects from other solids. The three CSG operators are Union, Intersection, and Difference. Each operator acts upon two objects and produces a single object result. By combining multiple levels of CSG operators, complex objects can be produced from simple primitives.
The union of two objects results in an object that encloses the space occupied by the two given objects. Intersection results in an object that encloses the space where the two given objects overlap. Difference is an order dependent operator; it results in the first given object minus the space where the second intersected the first.