A prism can be:

**straight**: when the side edges are perpendicular to the base planes;**oblique**: when the side edges are oblique to the base planes.

Look:

straight prism

oblique prism

We call a regular prism every straight prism whose bases are regular polygons:

regular triangular prism

hexagonal regular prism

Note: The faces of a regular prism are congruent rectangles.

Next: Prism Section