Meteors or meteorites are bits of rock (like granite) and ice - usually a mixture of rock and iron and nickel but sometimes just rock or just iron - from out in space that get sucked into the gravity of the Earth and fall through our atmosphere to the ground. Usually this is because a comet has passed close enough to the Earth for Earth's gravity to grab some of its material. A meteor is the same thing as a shooting star or a falling star - they're not really falling stars, but some people call them that.
Meteors look like stars as they fall because when they hit Earth's atmosphere the friction of the rock rubbing against the atmosphere causes heat and light, like a fire. This heat melts all the ice off the meteor.
Most meteors are tiny, the size of pebbles, and most of them fall into the ocean, because more of the Earth is ocean than there is land. Even if they fall on land, these tiny meteors don't do any harm. Sometimes, though, much larger meteors do fall to Earth. One really huge meteor, about eight miles across, smashed into the Earth about 65 million years ago, where it made a huge crater and sent thousands of tons of dust up into the air. As a result of this meteor, Earth got much cooler for a while, and most of the dinosaurs died.