The term MMO is an acronym for the phrase, Massively Multiplayer Online Game. These computer games are distinct because thousands, or even millions, of players can play simultaneously. MMOs are played on the Internet and revolve around a single or small group of virtual worlds hosted by massive servers. They can also be known as MMORPGs or Massively Multiplayer Role Playing Games.
MMOs are popular largely because they enable players to cooperate and or compete with each other within the virtual world, controlling their unique avatar. A few important characteristics of MMOs are that they typically require players to spend enormous amounts of their time playing the game, but also can promote meaningful interaction between people as they cooperate to complete game challenges. Furthermore, most MMOs demand a monthly or yearly subscription fee, as a means of profit or to help maintain/develop the game. Some examples of MMOs are Second Life and World of Warcraft.
- http://www.worldofwarcraft.com/index.xml World of Warcraft Homepage