MOO, or Multi-User Dungeon Object Oriented, is a type of online text-based game that allows multiple players to interact in a virtual world. Players can explore, create, and manipulate objects within the game environment, often using a programming language to enhance their experience. MOO games are known for their emphasis on social interaction and creativity. The first MOO was created in 1990 by Stephen White at Stanford University. Since then, many variations have emerged, allowing players to build their own worlds and share them with others. MOO environments often include elements of role-playing, storytelling, and collaborative building.