Below is a cutaway photo of the AeroTech Initiator rocket. Note it has several features not found in smaller hobby rockets.

One interesting thing is that as large and as complex as rockets get, they're still just variations on this basic design. There are fundamental physical principles which restrict what a stable and efficient rocket will be like. Of course, details of design and selection of materials differ widely, but most rockets really are "rocket shaped" and made up of these basic pieces.