Theory:

Polygons are classified according to the number of sides (or vertices) as follows:
Th_2.1.png
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:
Th_2.2.png
 
All the above polygons have at least one angle is more than \(180°\). So they are concave polygons.
Example:
Th_2.3.png
 
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:
1.png
 
In the above polygons, each of the sides and angles is equal. So they are regular polygons.
 
Th_2.5.png
 
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.