The Sh2 catalog is a collection of astronomical objects known as HII regions, which are areas of ionized hydrogen in space. It was compiled by the astronomer Sh2 (Shaw) and includes various nebulae and star-forming regions. The catalog serves as a valuable resource for astronomers studying the formation and evolution of stars. Each entry in the Sh2 catalog is designated with a number, such as Sh2-101, and provides information about the object's location, brightness, and physical characteristics. These regions are often associated with young, hot stars that emit ultraviolet light, causing the surrounding gas to glow.