Major changes are coming to The Division, and in order to test these changes there's a Public Test Server on PC for update 1.5 and the new Survival DLC. Basically the game turns into a survival sim where you'll need to scavenge for supplies and manage your body temperature. There are 24 players on the LZ map and you can choose between PvP and PvE mode. Obviously you won't be able to shoot other players in PvE, and the rewards in PvP are 20% better (but obviously the risk of dying is much higher).
Ubisoft are currently running a stream on Twitch showcasing Survival.
Update 1.5 and Survival is quite a big deal, and you can read up on what it means over on Reddit.