Fortnite Battle Royale, also known simply as Fortnite, is an immensely popular battle royale style shooter developed by Epic Games. It's available on a wide variety of platforms: PC (Windows and macOS), Xbox One, Xbox Series X/S, PlayStation 4, Playstation 5, Nintendo Switch, iOS and Android.
Like many battle royale games, Fortnite sees 100 players skydive - in this case, from a flying bus - onto a large sandbox-style island, where they must scramble to find equipment and weapons to fight off the other players. But there's not just the threat of other players looming, the playable area of the map will also steadily shrink, to bring the players closer and closer together for the final fight. Outside of this arena rages "the Storm", which will inflict damage on any player stepping into it.
You can play the game solo, with a friend but also in a group of up to 4 players. The last player or team to survive, wins the game.