If you remember from last week, most of the meteors we see in a meteor shower are actually tiny grains of dust or rock which are burning up in our atmosphere. Since they're so small, they very rarely make it through to the ground. Occasionally, though, something bigger will hit the Earth. Instead of a tiny grain of dust, maybe it's as big as a pebble, or even a large rock. These meteors are big enough that even though their outsides get burned up as they fall through the atmosphere, there's still some rock left by the time they hit the ground and are called meteorites.
Scientists are very excited to study meteorites.
Some of the meteorites which make it through the Earth's atmosphere are made out of rock, but many more are made out of metal. This probably is because metal is stronger and can survive the trip through the Earth's atmosphere without burning up. Scientists think that most meteorites are pieces of material left over from the formation of the solar system. Some of them contain very simple, primitive materials, such as those found in the asteroid belt between Mars and Jupiter. So until we can go take sample rocks from all the different places in the solar system, scientists have to make do with studying meteorites.