To start with, the ignition and afterwards, a sustained supply of fuel and oxidant.
A combustion chamber is where combustion occurs in a controlled fashion. Because the basic idea of a rocket is burning fuels and directing them in the opposite direction to that of travel, a controlled burning - as happens in the combustion chamber - is exactly what a rocket needs to work.
Florence
Thrust from the combustion of rocket fuel.
combustion
combustion
Chemical rocket
Chemical rocket
The force of the combustion pushes on the interior of the rocket. The combustion releases through the rear exhaust, causing the rocket to move forward.
The rocket pushes back on the gas.
The rocket pushes back on the gas.
Rockets exert force at the upper part of the combustion chamber. This pushes the rocket forward.
Rockets are propelled forward by thrust generated by the combustion of rocket fuel and controlling the direction of the exhaust.