Comets are small celestial bodies made of ice, dust, and rocky material that travel through space. They originate from the outer regions of the solar system, particularly from areas known as the Kuiper Belt and the Oort Cloud. When a comet approaches the Sun, the heat causes its ice to vaporize, creating a glowing coma and often a tail that points away from the Sun. Comets can vary in size and composition, with some being just a few kilometers across. They have highly elliptical orbits, which means they can take many years or even centuries to complete a single trip around the Sun. Famous comets include Halley's Comet, which is visible from Earth approximately every 76 years.