A genre of video game where the player has a large world they can explore. It really started to gain popularity with the Xbox 360/PlayStation 3 as technology had improved to the point where developers could exploit the hardware to it's fullest for that genre.

Many RPGs use open worlds. Recently they have been criticized as developers use them to pad out content that is otherwise not complex, deep, or engaging. Ubisoft is notorious for this with their latest Assassin Creed games.

Famous examples include:
Skyrim
Borderlands
Cyberpunk 2077