Faces, edges and vertices

Cut along some edges of a cardboard box and press it flat: what you get is a net, a flat pattern that folds back into the solid.

Every solid with flat sides has three things to count:
- Faces: the flat surfaces.
- Edges: the lines where two faces meet.
- Vertices: the corners, where edges meet.

A cube has 6 faces, 12 edges and 8 vertices. A triangular prism (a Toblerone box) has 2 triangles and 3 rectangles: 5 faces, 9 edges and 6 vertices.