An online game is a game played over some form of computer network. This almost always means the Internet or equivalent technology, but games have always used whatever technology was current. Gamers used modems before the Internet, and hard wired terminals before modems.
The expansion of online gaming has reflected the overall expansion of computer networks from small local networks to the Internet and the growth of Internet access itself. Online games can range from simple text based games to games incorporating complex graphics and virtual worlds populated by many players simultaneously.
Many online games have associated online communities, making online games a form of social activity beyond single player games. Massively multiplayer online games were made possible with the growth of broadband Internet access in many developed countries, using the Internet to allow hundreds of thousands of players to play the same game together. Many different styles of massively multiplayer games are available.
Today online gaming is so popular that there are sites that are not actual gaming sites but rather are sites where people share ideas about how to progress through the game or where people read reviews and ask questions and share news about a particular game.