Polygon

A polygon is a flat, two-dimensional (2D) shape with straight sides that is fully closed (all the sides are joined up). The sides must be straight. Polygons may have any number of sides.

-A regular polygon is a polygon in which all sides are of all the same length and at the same angles.
-An irregular polygon is a polygon with sides and/or angles of different lengths and sizes. 

 

Some different types of polygon (https://en.wikipedia.org/wiki/Polygon#/media/File:Polygon_types.svg)