A frustum is a three-dimensional geometric shape that results from slicing the top off a cone or a pyramid. It has two parallel circular or polygonal bases, with the top base being smaller than the bottom base. The sides of a frustum are typically slanted, connecting the edges of the two bases. Frustums are commonly found in everyday objects, such as cups, lampshades, and certain types of containers. They are important in various fields, including architecture, engineering, and mathematics, as they help in calculating volumes and surface areas for practical applications.