How does propulsion work?

What is a propellant?

Rockets work because every action has an equal and opposite reaction (according to Sir Issac Newton's third principle). In order for the rocket to rush forward, something has to rush backwards. That thing is the propellant. The propellant is a material that spews out of the back of the spacecraft giving it thrust, or a push forward.

Often the propellant is a kind of fuel which is burned with an oxidizer to produce large volumes of very hot gas. These gasses expand until they rush out of the back of the rocket, making thrust. Sometimes the propellant is not burned, but pushed directly out of the spacecraft, making thrust. In ion propulsion, the propellant is made of electrically charged atoms, which are magnetically pushed out of the back of the spacecraft. For smaller attitude control thrusters, a compressed gas is pushed out of the spacecraft.

How are rockets designed?
What is the difference between an ion engine and a conventional one?
How does solar electric propulsion (ion propulsion) work?
How do conventional rockets work?

Every action has an equal and opposite reaction?
What is thrust?
What are the types of rocket propulsion?

How is rocket propulsion different from jet propulsion?
What are some rocket propellants?