3-dimensional figures occur everywhere in the world around us, especially in fields such as architecture.
A prism is a 3-dimensional figure that has two parallel, congruent bases connected by lateral faces. The lateral faces of a prism are always parallelograms and are usually rectangles. A prism is named by the shape of its base. So, a prism with a rectangular-shaped base is called a rectangular prism. Likewise, a prism with a hexagonal-shaped base is called a hexagonal prism.
A pyramid is a 3-dimensional figure that has one base. The lateral faces of a pyramid are triangles that meet at one point, which is called the vertex. Like prisms, pyramids are named by the shape of their base. A pyramid with a square base is called a square pyramid.
A cylinder is like a prism, but the bases of a cylinder are circles instead of polygons. A cylinder has two circular bases and a curved lateral surface. Since the surfaces of a cylinder are not polygons (they have round edges and are not always planar figures), we call them surfaces instead of faces.
Consider the barn and silo shown. The silo is in the shape of a cylinder with a half-dome roof. The barn is a prism with a seven-sided polygon as the base, so we can call the barn a heptagonal prism.