What makes a prism?

Answer 1

In its most generalised form it comprises two connected, congruent and parallel faces: these faces are called the bases. In a right prism, the bases are at right angles to the length of the prism. In a polyhedral prism, all faces are polygons and, in such a case, the faces joining the bases are quadrilaterals. In the very special case of a right polyhedral prism, the bases are polygons and the lateral faces are rectangles.

Answer 2

a prism is a prism if it can be cut into even cross sections. that is, if you sliced it in half, both faces would look the same. so, a cube is a prism but not a cone.