Massively multiplayer online (MMO) refers to a genre of video games that allow large numbers of players to interact and play together in a virtual world, often featuring persistent game environments. These games typically incorporate social elements, enabling players to form communities, collaborate on quests, and compete against one another. MMOs can encompass various genres, including role-playing games (RPGs), first-person shooters, and real-time strategy games, creating diverse experiences for players around the globe.