What is a plane figure in geometry?

A two-dimensional figure, also called a plane or planar figure, is a set of line segments or sides and curve segments or arcs, all lying in a single plane. The sides and arcs are called the edges of the figure. The edges are one-dimensional, but they lie in the plane, which is two-dimensional. The triangle, the pentagon, the hexagon and the circle are just a few plane figures. Prisms and pyramids, for instance, are three-dimension figures.