Grand Theft Auto III was released, helping to popularize open-world and mature-content video games.

Grand Theft Auto III
Grand Theft Auto III is a 2001 action-adventure game developed by DMA Design and published by Rockstar Games. It was the first 3D game in the Grand Theft Auto series. Set in Liberty City, loosely based on New York City, the story follows Claude, a silent protagonist who becomes entangled in a world of crime, drugs, gang warfare and corruption. The game is played from a third-person perspective and its world is navigated on foot or by vehicle. Its open world design lets players freely roam Liberty City.
Open world
In video games, an open world is a virtual world in which the player can approach objectives freely, as opposed to a world with more linear and structured gameplay. Notable games in this category include The Legend of Zelda (1986), Grand Theft Auto V (2013), Red Dead Redemption 2 (2018) and Minecraft (2011).