Massively multiplayer online game

An online video game in which large numbers of players interact in a shared virtual world, often one that continues to exist between play sessions.

Client–server model: A computing architecture in which client devices request services and data from a central server. Game clients exchange actions and world updates with servers that coordinate shared play.
MUD: A text-based multiplayer virtual world in which participants interact through typed commands. MUDs established persistent, social play before graphical online worlds became common.
Player versus environment: A game mode in which players cooperate against computer-controlled opponents or challenges. Quests and dungeon encounters commonly organize cooperative activity in these games.
Online community: A group whose members interact and form relationships through internet-based platforms. Repeated play gives communities shared routines, identities, and long-term relationships.
Persistent world: A virtual environment whose state continues to change and remain available when individual users are absent. Its continuing state distinguishes many online worlds from matches that reset after each session.
Multi-user dungeon: A text-based role-playing game in which multiple participants explore a shared virtual environment. This early MUD form combined cooperative play, exploration, and persistent characters.
Player versus player: A game mode in which human players compete directly against one another. Many shared worlds add arenas, duels, or open-world combat alongside cooperative play.
Virtual world: A computer-generated environment in which users interact through digital representations of themselves. These games are a prominent form of inhabited, interactive virtual world.
Instancing: A technique that creates separate copies of a game area for different groups of players. Private copies ease crowding while preserving shared-world play elsewhere.
Meridian 59: A 1996 online role-playing game often identified as one of the first graphical MMORPGs. Its commercial release helped establish the graphical online role-playing format.

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