Video Games Encyclopedia

A massively multiplayer online game (MMOG, or more commonly, MMO) is an online game with large numbers of players, often hundreds or thousands, on the same server. MMOs usually feature a huge, persistent open world, although some games differ. These games can be found for most network-capable platforms, including the personal computer, video game console, or smartphones.
MMOs can enable players to cooperate and compete with each other on a large scale, and sometimes to interact meaningfully with people around the world. They include a variety of gameplay types, representing many video game genres.