STOP sign
A practical example of a convex polygon is a STOP sign. Since it has 8 equal sides, it is called an regular octagon. All the interior angles are equal and each is less than 180°.
If each angle of a polygon is less than 180° (straight angle), then it is called a convex polygon.
All the diagonals of a convex polygon lie entirely inside the polygon.
In the below figure, ABCDEF is a convex hexagon and PQRST is a convex pentagon.
(The diagonals are shown as dotted lines).