Rockets take people, spaceprobes and satellites up into space. In a rocket engine special rocket fuel burns to produce gases which rush out at the back, pushing the rocket forwards. Rockets have to carry big fuel tanks with them up into space. As the fuel is used up these tanks fall back to earth, sometimes to be used again.
Some rockets send space probes into space to find out about other planets.
These probes may even drop robot craft called Landers down onto the surface of the planet. The lander may take soil samples, test the air and send pictures of the planet back to us on earth. They send back information on the weather, pollution and even the rate at which tropical rainforests are being destroyed. They also send TV and radio signals around the earth. Landers landed on Mars but didn't find any life.