Fortnite is an online video game created in 2017, developed by Epic Games, and released as different software packages having different game modes that otherwise share the same general gameplay and game engine. The game modes include Fortnite: Save the World, a cooperative shooter-survival game for up to four players to fight off zombie-like creatures and defend objects with fortifications they can build, and Fortnite Battle Royale, a free-to-play battle royale game where up to 100 players fight in increasingly-smaller spaces to be the last person standing. Both game modes were released in 2017 as early access titles; Save the World is available only for Microsoft Windows, macOS, PlayStation 4, and Xbox One, while Battle Royale has been released for those platforms, as well as Nintendo Switch, iOS and Android devices.
While both games have been successful for Epic Games, Fortnite Battle Royale became a resounding success, drawing in more than 125 million players in less than a year, and earning hundreds of millions of dollars per month, and since has been a cultural phenomenon. (Source)