A massively multiplayer online (MMO) game is a game played via the Internet by hundreds, if not thousands, of people at once. It is different from traditional one- or two-player games in both scale and game-play method. By definition, an MMO supports many players — while it is possible for just a few to play at once, MMO systems typically have hundreds or thousands of people playing simultaneously. When this game type was first created, it could only be played on a computer using an Internet connection, but that has changed as gaming systems have advanced. Many MMOs have one or more consistent online worlds where people meet and play.
An MMO is any game that is able to support a massive number of players at once, regardless of genre. Small MMOs usually host hundreds of players, while larger ones can host thousands or even millions of people simultaneously. Having this many people playing at once can slow down processing — loading each player’s character and the character's clothing, actions, conversations and movements takes a lot of memory — so most MMOs are split over different servers. Each server typically will host a small segment of the entire player base.
Connecting this many people through a single gaming system would be impossible, because the resources needed for this task would be unprecedented. Instead, MMO games rely on the Internet to connect players. Most MMOs also will only allow only person to play at a time per computer or gaming system, so households with more than one player wanting to join the game at the same time will need more than one system.
In the early days of the MMO, only computers could be used to play, because they were the only devices to have Internet access. As gaming systems advanced, many also gained access to the Internet. The computer still is the most common system for playing MMOs, though these games can now be played from many different platforms.
The majority of MMO games feature one or several consistent worlds where everyone is able to meet, chat and play. While most MMOs have players start in the same area, some have different starting points. This usually is based on the type of character the player creates, but it also may be selected at random by the game.