If the horizontal velocity is higher than the critical velocity but lower than the escape velocity, the satellite takes an elliptical orbit around the earth. The initial orbit of a satellite is called the transfer orbit. Depending on their various applications, satellites need to be placed in other orbits. Small firings are done from the satellite itself by which it gets additional velocity. This additional force is able to get the satellite into another path or orbit.
Rockets work on the principle of Newton's third law of motion.
The law states that every action has an equal and opposite reaction. In a rocket, the fuel is fired in such a manner that it escapes with force in a downward direction. This is action. The reaction in the opposite direction is that the rocket with its payload is able to go vertically upwards. Depending on the amount of fuel fired, the rocket will get its vertical velocity.