Mudlib

A MUD (/ˈmʌd/; originally Multi-User Dungeon, with later variants Multi-User Dimension and Multi-User Domain), is a multiplayer real-time virtual world, usually text-based. MUDs combine elements of role-playing games, hack and slash, player versus player, interactive fiction, and online chat. Players can read or view descriptions of rooms, objects, other players, non-player characters, and actions performed in the virtual world. Players typically interact with each other and the world by typing commands that resemble a natural language.

Traditional MUDs implement a role-playing video game set in a fantasy world populated by fictional races and monsters, with players choosing classes in order to gain specific skills or powers. The objective of this sort of game is to slay monsters, explore a fantasy world, complete quests, go on adventures, create a story by roleplaying, and advance the created character. Many MUDs were fashioned around the dice-rolling rules of the Dungeons & Dragons series of games.

Such fantasy settings for MUDs are common, while many others have science fiction settings or are based on popular books, movies, animations, periods of history, worlds populated by anthropomorphic animals, and so on. Not all MUDs are games; some are designed for educational purposes, while others are purely chat environments, and the flexible nature of many MUD servers leads to their occasional use in areas ranging from computer science research to geoinformatics to medical informatics to analytical chemistry. MUDs have attracted the interest of academic scholars from many fields, including communications, sociology, law, and economics. At one time, there was interest from the United States military in using them for teleconferencing.

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Wikipedia