A comet is a ball of mostly ice that moves around in outer space. Comets are often described as "dirty snowballs". They are very different from asteroids. The orbital inclinations of comets are usually high and not near the ecliptic where most solar system objects are found. Most of them are long-period comets and come from the Kuiper belt. That is very far away from the Sun, but some of them also come near enough to Earth for us to see at night. 