There are four triangular faces on a tetrahedron. A face describes an individual surface on an object. On the tetrahedron, people can only see three of the four faces.
To create a tetrahedron, three triangles come together and they meet at a vertex. The point where at least two straight lines come together is the vertex. When analyzing the ordinary convex polyhedra, the tetrahedron is the simplest of all of them. It is also the only one with less than five faces. It is a type of pyramid with triangular faces that come together at a common point and it has a flat polygon base.