MMO stands for Massively Multiplayer Online, Basically a game where there is a world and it will exist with or without you and you play with a lot of players in that said world, There is no number attached to MMO rather its a feeling of being part of a massive event or game.
MMO games are designed to be shared world and is playable with many players. Most MMOs encourage social interactions, trading and playing with 1 another. Its a world where gamers can interact with other gamers from around the world.
