A polygon can be any number of shapes. A polygon is a two dimensional shape made of at least 3 straight lines that do not cross and is a closed shape. Examples of polygons would include triangles, squares, rectangles, hexagons, and octagons.
Regular polygons are made when all sides and angles of the shape are the same size. When the sides or angles are different sizes, the polygon is said to be irregular. Any shape with a curved side is not a polygon.
Other types of polygons include convex, where all interior angles are less than 180 degrees, and concave, where one or more interior angles measure more than 180 degrees.