This part is perhaps a bit too detailed, containing quite a few lines explaining the difference between convex and concave and giving an example in a note.

"For a convex regular polygon, the polygon corners are located on a single circle that has its center in the center of the polygon. In a concave regular polygon, the polygon corners are located on two such circles with a different radius, where corners that are located next to each other are located on different circles."
...
"Note: An example of a convex regular polygon is a hexagon. An example of a concave regular polygon is a star. "