Prism 3D algorithm can be used for meshing prisms, i.e. 3D Shapes defined by two opposing faces having the same number of vertices and edges and meshed using the 2D Projection algorithm. These two faces should be connected by quadrangle "side" faces.
The opposing faces can be meshed with either quadrangles or triangles, while the side faces should be meshed with quadranglees only.
As you can see, the Prism3D algorithm permits to build and to have in the same 3D mesh such elements as hexahedrons, prisms and polyhedrons.