A comet is a small celestial body that orbits the Sun. Comets are made up of ice, dust, and rocky materials. When a comet approaches the Sun, the heat causes the ice to vaporize, creating a glowing coma and often a tail that points away from the Sun. This phenomenon makes comets visible from Earth. Comets are believed to originate from two main regions in the solar system: the Kuiper Belt and the Oort Cloud. They can have highly elliptical orbits, which means they can travel far from the Sun and then return, sometimes after many years.