The long-awaited survival mode beta for Fallout 76 arrives today, effectively splitting the game in two. Upon starting the game, you will now choose to play in adventure mode, for the standard Fallout 76 experience, or the new survival mode beta, where PvP is the default setting, there are fewer restrictions, and greater rewards.
In survival mode, other players are considered hostile (unless their weapons are holstered, at which point their nameplates will indicate they are 'neutral'). Players can be attacked at any point and will take full damage immediately. There's no 'slap' damage and they do not need to return fire—the PvP switch in survival mode is fully in the 'on' position.
Other features of survival mode include a 20% bonus for any XP gained, which is a pretty big draw for taking your chances in a more dangerous world. When killed in PvP, players drop not just junk but also random items from their Aid inventory, and they can place a bounty on their killer using their supply of caps (the minimum being 200). Players with bounties are the only ones whose locations will be shown on the map.
After dying in survival mode, you can only respawn at Vault 76, your camp, or at train stations. Fast-travel is also restricted to those locations, plus any workshops you currently own. Leaderboards will let you see how you're doing in categories like longest life, most kills, bounties collected, and so on.
Over in adventure mode, meanwhile, slap damage has been removed. When attacking another player they will now take zero damage unless they fight back. So, if someone is shooting you and you don't want to take part in PvP, feel free to completely ignore them until they're out of ammo or they give up completely.
You can read more here in the official patch notes. Patch notes from earlier updates can be viewed on the following pages.