Antiprism

It is like a prism, but the two ends (identical polygons) are twisted and connected by a band of alternating triangles.

Here is an octagonal antiprism: there are two identical parallel octagons, one is twisted, then they are joined by triangles.

The twist is usually 180°/(number of sides), so the octagonal antiprism has a twist of 180/8 = 22.5°.

Below is a square antiprism, with a 180°/4 = 45° twist.