A comet is a smaller celestial body orbiting the sun, often with a tail made of debris. Debris from a comet can turn into a meteor, which means that is has entered into Earth's atmosphere and burns due to the friction with the Earth's atmosphere. If a meteor is large enough, it can survive this fall into Earth's atmosphere and strike the Earth, on land this would leave an impact crater, or a collision site where the meteor met the surface. This can also happen in water, but may be difficult to see and may not leave an impact crater. Simply, Comet to Meteor to Impact crater.