The simplest way I can explain faceting is that it takes a familiar polyhedron’s vertices, and then connects them in unusual ways, so that you obtain different edges and faces. If you take the convex hull of a faceted polyhedron, it returns you to the original polyhedron.
This was created using Stella 4d, software available (including as a free trial download) right here: http://www.software3d.com/Stella.php.