Comets are small, icy rock bodies that did not get incorporated into  the Sun or the planets. They comprise of a nucleus, coma, hydrogen cloud, dust tail, and ion tail.

Comet Kohoutek around the Sun

Comet Hyakutake by Shigemi Numazawa (NASA)

Comet in orbit

 

Comet Collision Illustration

Comet Hartley 2

Satellite & Comet Illustration

 

Woodcut of Comet Encounter