what is the difference between a pentagonal prism and a pentagonal pyramid???????????

A pentagon is a 5 sided figure. pentagonal prism is a 3D structure where the top and the bottom face is a pentagon and the side faces are 4 sided figures (it may be a square or a rectangle) whereas pentagonal pyramid is a structure where only the bottom face is a pentagon and the top face is reduced to a point and so the side faces are 3 sided figures.