MUD

A MUD (/mʌd/; originally multi-user dungeon, with later variants multi-user dimension and multi-user domain)[1][2] 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 live 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. https://en.wikipedia.org/wiki/Multi-user_dungeon