A meteor is a space rock that hits the atmosphere of the Earth. It's also another word for a shooting star.
There are a lot of bodies in space, such as suns, planets, and moons. Those are all rather large, but there are smaller bodies too, such as meteors. A meteor is a smaller body in space that collides with the Earth or another planet. You can also use this word for the light caused by such an impact: a meteor is a shooting star. Many meteors are caused by comets that have decayed.