A prismatoid is a polyhedron where all vertices lie in two parallel planes. Under some circumstances I forget it is called a prismoid. Some particular families of prismatoids:
Prisms, where the polygons in each plane are congruent and joined by rectangles or parallelograms;
Antiprisms, where the polygons in each plane are congruent and joined by an alternating strip of triangles;
Frustrums, where the polygons are similar and joined by trapezoids;
Pyramids, where one plane contains only a single point;
Cupolas, where the polygon in one plane contains twice as many points as the other and is joined to it by alternating triangles and rectangles.
