3D solid objects often start as one of several basic shapes, or primitives, that you can then modify and recombine.
About Solid Primitives
You can create several basic 3D shapes, known as solid primitives: boxes, cones, cylinders, spheres, wedges, pyramids, and tori (donuts).
By combining primitive shapes, you can create more complex solids. For example, you can join two solids, subtract one from the other, or create a shape based on the intersection of their volumes.