So, the asteroid belt is assumed to be the last part of a planet, and it orbits the sun, somewhere between the planets Mars (4th from the sun) and Jupiter (5th from the sun). Although asteroids can come from anywhere in the solar system, and in fact, from beyond our solar system in certain instances, the asteroid belt is the primary source of asteroids we here on Earth concern ourselves with.
Asteroids come in three different categorizations: they can be stony, or they can be carbonaceous, or they can be metallic. Asteroids also range in mass. Some are around the mass of a small cabin, while others can be absolutely gigantic!