What is a concave polygon

The video tutorial explains the difference between convex and concave polygons. It describes how convex polygons have sides that do not intersect the interior, while concave polygons have sides that do. The tutorial provides a visual test to determine if a polygon is concave by extending its sides and checking for intersections within the interior. The concept of concavity is likened to an indent, similar to a cave, to help students remember the difference.

What happens to the lines when they are extended in a concave polygon?

What analogy does the teacher use to describe a concave shape?