A rocket is a vehicle or device that moves by pushing hot gases out of one end at tremendous speed. Think of a balloon: when you blow it up and let it go, the air rushing out one end pushes the balloon in the opposite direction. A rocket works on this same principle, called thrust, but instead of air, it burns fuel to create powerful exhaust gases that shoot out the back, launching the rocket forward.

Rockets can travel where airplanes cannot, including outer space, because they carry their own oxygen supply and don't need air to push against. The Saturn V rocket that carried astronauts to the Moon stood as tall as a 36-story building and generated enough thrust to lift 6.5 million pounds. Modern rockets launch satellites that help you use GPS, deliver supplies to the International Space Station, and make space exploration possible.

The word rocket can also describe something moving extremely fast. When your little brother goes rocketing down the hallway, he's running at top speed. Scientists study rocket science, which has become a phrase people use when something is supposedly super complicated, though real rocket scientists will tell you that with enough study and practice, you can understand how rockets work.