A special kind of convex polygon is called a regular polygon:

DEFINITION:    A regular polygon is a convex polygon in which all sides are congruent.

Another way to define a regular polygon is to state that its sides are congruent and its angles are congruent.  If a polygon is not regular, then it is called irregular.

Examples:

Concave Polygons:

Convex, Irregular Polygons:

Regular Polygons: