The Arp Catalog is a collection of galaxies compiled by astronomer Halton Arp in 1966. It includes 338 peculiar galaxies, which are unusual in shape or structure, and aims to help astronomers study galaxy formation and evolution. The catalog is widely used in astrophysics for research and observation. Each entry in the Arp Catalog is designated with a number, such as Arp 220, which refers to a specific pair of interacting galaxies. The catalog highlights various phenomena, including galaxy collisions and interactions, providing valuable insights into the dynamics of the universe.