Theory:

Polygons are classified according to the number of sides (or vertices) as follows:
Important!
Here $$n$$-gon denotes the polygon with $$'n'$$ sides and $$'n'$$ vertices.
Example:
$$35$$-gon is a polygon which is made up of $$35$$ vertices and $$35$$ sides.
Concave and convex polygon: If each of the interior angles of a polygon is less than $$180°$$, then it is called a convex polygon. If at least one angle of a polygon is more than $$180°$$, then it is called a concave polygon.
Example:

All the above polygons have at least one angle is more than $$180°$$. So they are concave polygons.
Example:

In the above polygons, each of the interior angles is less than $$180°$$. So they are called convex polygons.
Regular and irregular polygon: A regular polygon is a polygon whose all sides and all angles are equal. Thus, a regular polygon is both equiangular and equilateral.
Example:

In the above polygons, each of the sides and angles is equal. So they are regular polygons.

In the above polygons, at least one side measures are different and at least one angle measures are different when compared to others. So they are irregular polygons.