what are comets?

A comet is a celestial body made of ice, dust and gas that forms in the outer solar system beyond the outermost planet. Some of these objects periodically, since the time of their initial perturbation from the ring of comets (otherwise known as the Oort Cloud) where they formed, travel into the inner solar system anywhere from toward the sun or possibly as far as the farthest planet from comets starting point. Comets introduce or provide more material (solid and liquid) and fuel for stars and planets that such bodies transpire out to space. This is the case more frequently with meteroids. Asteriods and comets usually provide extra material in passbyes rather than impacts, today.