What are concave and convex polygons?

Polygons can be classified as convex or concave. In a convex polygon, every diagonal of the figure passes only through interior points of the polygon. In a concave polygon, at least one diagonal of the figure contains points that are exterior to the polygon.

Convex:every diagonal passes only through interior point of a polygon
Concave polygon:it has at least one diagonal contains points that are exterior to the polygon

concave;it is an angle pointing inwards
convex;a convex polygon that has all its interior angles pointing outwards

A convex polygon has no angles pointing inwards. More precisely, no internal angle can be more than 180°. If any internal angle is greater than 180° then the polygon is concave. ( Think: concave has a “cave” in it) Convex.