Here's how it works:

1. Burning Fuel: A rocket engine burns fuel, typically a combination of liquid hydrogen and oxygen. This combustion creates hot, expanding gases.

2. Nozzle Expansion: These gases are directed through a nozzle, which is shaped to accelerate the gases and increase their velocity.

3. Newton's Third Law: As the hot gases are expelled out of the nozzle at high speed, they exert a force in the opposite direction. This is explained by Newton's Third Law of Motion: "For every action, there is an equal and opposite reaction."

4. Thrust Generation: The force pushing the gases out of the nozzle is the thrust, which propels the rocket forward.

Essentially, a rocket works by pushing hot gas out the back, and the reaction force from this push drives the rocket forward.