3D shapes, they have 3 dimensions ... You're now a square based pyramid with 4 triangular faces and a square face for your bottom. You can get pyramids with different shaped bases.

It details the formulas used to calculate their volumes, emphasizing the relationships between these shapes. For example, the volume of a pyramid is one-third that of a prism with the same base ...

A 3D shape with all straight edges and flat faces is a polyhedron. Other 3D shapes with least one curved surface are not polyhedra. A 3D shape with regular polygonal faces, meeting at equal angles ...