Here's how it works:

* Rocket engines burn fuel (usually a combination of liquid hydrogen and oxygen) in a combustion chamber.

* This burning creates hot, expanding gases at incredibly high pressure.

* These gases are then expelled out of a nozzle at high velocity.

* This expulsion of hot gas creates an equal and opposite force (Newton's Third Law of Motion) that pushes the rocket upwards.

So, while the rocket engine doesn't actually "push" against the ground like a car engine, it uses the force of the expelled gases to generate thrust, propelling the rocket into the air.