One of the Archimedean solids, with 6 square faces and 8 triangular faces. It can be formed by cutting off the corners of a cube to obtain a polyhedron whose vertices lie at the midpoints of the edges of the original cube.

http://www.scienceu.com/geometry/facts/solids/java/cubeocta.html A cuboctahedron which can be manipulated to see its shape fully.