A comet is a small celestial body composed primarily of ice, dust, and rocky material. When a comet approaches the Sun, it heats up, and the ice vaporizes, creating a glowing coma and often a tail that streams away from the Sun due to solar wind. This unique feature distinguishes comets from other celestial bodies like asteroids, which are primarily made of rock and metal. Comets are believed to originate from the outer parts of the Solar System, such as the Kuiper Belt and the Oort Cloud, and their orbits can take them close to the inner solar system, producing spectacular displays.