An online game is a game played over some form of computer network. Generally, it refers to a set of games in which many players play some certain roles and change the setting in a virtual world based on certain rules to gain entertainment and interaction through a computer network, now generally the Internet. The development of online games is, to some extent, based on the development of technology.

Due to the historical leap from small local networks to the Internet, online games have undergone fundamental changes, hence attracted more and more players. There are different kinds of online games for web surfers to enjoy. For example, one can choose to play the simple text based games, while others may prefer games that contain a virtual world created by many players simultaneously. Online games may even create an online community which involves social activities compared with single player games. Online games can be divided into two categories in terms of usage:

Browser games, namely web games, require no download of Client. That is to say, one can enjoy the game anywhere at any time only if he has access to the Internet. Browser games contain all kinds of games as well, including simulation games, role-playing games, social network service and etc.

Client-based games are provided by companies through servers and players enjoy the games through a Client connected to the servers. Most online games belong to this category. In Client-based games, most players have a virtual identity and all the deposit and game information are recorded into the servers. Many Client-based games, like World of Warcraft, Battlefield and Final Fantasy are very popular with web-users.

As science and technology develops, free online games have also undergone fundamental changes. More and more people are attracted by online games with more convenient access to the Internet. With no exaggeration, online games will mean much more than a game to those web-users. Actually many players have viewed online games as a way of life. The growing popularity of online games demands more development of new and creative online games as well as more governance.