There is a new experimental map in PlayerUnknown's Battlegrounds. In order to get the key, you need to have a valid Steam account and a purchased copy of PUBG.
Savage is the new 4x4 map, which resembles the map from Fortnite. It's twice as small as Erangel, which makes it a lot more dangerous and faster. If you want to know which locations are the best to drop at and find the finest loot, then follow this guide for all the key locations on the Savage map.