Comets are pieces of meteors or asteroids which get attracted towards the earth due to its gravitational force.
Following are their characteristics :
1. On their way to the earth, they get burnt due to friction with atmospheric particles.
2. In the atmosphere, during friction, they appear as shining bodies with long tails which we call as falling stars.
3. Some comets are so big that they do not diminish completely and they hit the earth’s surface. At this point, they are called as meteors.
4. When they fall on the earth, they cause hollows on the earth’s surface.