PlayerUnknown's Battlegrounds or sometimes referred to as PUBG is a multiplayer online battle royale game where 100 players parachute onto an island and the last one alive wins. After being deployed you land on a map with no weapons or equipment and are forced to scavenge them from buildings or loot them from other players you kill.
Everyone is an enemy unless you are playing Duo or Squad matches and teamwork is forbidden. As you kill off other players and try to survive a 'Restricting the Play Area' message will appear on screen after a period of time to inform you that the safe area will gradually shrink from the outside edges, when this begins it forces the remaining players to move closer and closer to one another. If you stay outside the playable zone you automatically become eliminated from the tournament.