The base of a pyramid is typically a polygon. The most common type is a square base, which is the case for the well-known Egyptian pyramids. However, pyramids can also have triangular, rectangular, or even more complex polygonal bases.
The shape of the base defines the type of pyramid: for instance, a pyramid with a triangular base is known as a tetrahedron, while one with a square base is simply called a square pyramid. Regardless of the base’s shape, the defining characteristic of a pyramid is that its sides taper upward to meet at a single point, called the apex.
In summary, while pyramids may have various base shapes, the most recognized form features a square base, which allows for a stable and symmetrical structure.