Here are some common shapes:

Square = polygon with 4 sides
Circle = not a polygon
Triangle = polygon with 3 sides

Polygons:
closed plane figures 
made from line segments
      triangles (3 sides)    quadrilaterals (4 sides)

pentagons   (5 sides)hexagons  (6 sides)

heptagons  (7 sides) octagons  (8 sides)

Remember:

Shapes are Plane Figures    that lie on a flat surface.

Click on the shapes for practice.