QUESTION: 
How exactly does the rocket get launched? 

ANSWER from John L Callas on Decemebr 10, 1996:
Rockets use fuel that combust (burn) to release energy. The released energy
cause the gases from the combustion to expand. The expanding gases flow 
through a rocket nozzle which directs the force of expansion, called 
thrust, in one direction. Bcause of Newton's Third Law of Motion (action 
and reaction), this thrust pushes on the rocket and makes it go. 
This works in space as well as on the ground.