a multistage rocket is a rocket. a rocket could be a multistage rocket. all multi-stage rockets are rockets, but not all rockets are multi-stage. For example the space misstions. They are all multi...
At the very bottom is the nozzle, after that is the fuel. Depending on how big the rocket is and how much fuel it needs determines the size of the chamber
A solid or liquid propellant is typically oxidized, or burned inside a nozzle. The expansion of the fuel into the gaseous state provides thrust against the nozzle surface.
If you have a standard kit, the motor goes in the tube at the bottom so that the end of the motor with a clay nozzle sticks out. Place an igniter in the motor and (if you are using Estes or Quest...