What is an Asteroid?
Asteroid and Meteorite What's the Difference?
An asteroid which can be as small as a pebble or as large as 1000km in diameter is a rocky metallic object that orbits the sun.
They're believed to be left over from the formation of the solar system. Some believe asteroids are the remains of a planet that was destroyed in a massive collision many millions of years ago.
When an asteroid is on a collision course with Earth it's called a meteoroid. Should an asteroid enter Earth's atmosphere friction causes it to incinerate into a streak of light. The subsequent "fireball" better known as a "shooting star" is called a meteor.
If the meteoroid does not burn up completely whatever is left crashes into the surface of Earth. That object is a meteorite.