Meteorites are large masses from different solar system bodies and are composed of rock or sometimes metal. After travelling vast distances these objects enter the atmosphere and crash into the ground with great force. Many of these bodies are not observed falling but are instead found by accident or by skilled meteorite hunters specifically looking for these objects.
Most of these masses come from rather small bodies (up to several hundred kilometers in diameter but usually much smaller) that are found in the asteroid belt which is located in our solar system between Mars and Jupiter. These objects collide with one another or get catapulted towards Earth by the gravitational pull of the two planetary bodies within their vicinity.
The most prevalent meteorites found contain small, glassy nodules called chondrules and these are coined chondrites. These are, of course, not the only types of meteorites that fall to Earth, planetary meteorites also make up a small portion of these falling bodies as do pallasites and iron meteorites.