Great Comets are exceptionally bright comets that can be seen with the naked eye from Earth. They often develop long, glowing tails as they approach the Sun, which causes their icy nuclei to vaporize. This process creates a spectacular display, making them visible even during daylight in some cases. These comets are classified as "great" based on their brightness and visibility. Famous examples include Halley's Comet, which appears every 76 years, and Comet Hale-Bopp, which was visible for a record 18 months in the late 1990s. Great Comets provide valuable insights into the early solar system.