.hack//G.U. simulates a massively multiplayer online role-playing game; players assume the role of a participant in a fictional game called The World. While in The World, the player controls the on-screen player character, Haseo, from a third-person person perspective (with optional first-person mode). Within the fictional game, players explore monster-infested fields and dungeons as well as "Root Towns" that are free of combat. They also can "log-off" from the game and return to a computer desktop interface which includes in-game e-mail, news, and message boards, as well as desktop and background music customization options.
Source: Wikipedia, ".hack//G.U.", available under the CC-BY-SA License.