PvP is a Multiplayer feature in Fallout 76 (FO76). By engaging in hostile interactions with other Wastelanders, players can obtain equipment, experience and valuable items. For cooperative parties, see the Companions page.
Fallout 76 PVP Explained
What is PVP Mode
Players will be given the ability to swap in and out between players-versus-players and players-versus-environment, as they choose. As it describes, PvP's purpose is to fight other players so there won't be a lot of consequences in regards to killing others but balance changes may be implemented to prevent a one-sided battle. Upon death, players can rejoin the battle by selecting a spawn location on the map, losing a few scraps and bits of Junk (used to craft weapon mods etc) where they died.
In PvP mode, the caps you can acquire from killing another player is dependant on their level. Therefore a low-level player is a less desirable target. Players are also protected by the murder system. When a player first attacks another, they will deal only 'chip damage' (greatly reduced damage values). Only when the attacked player fires back will the players be able to hit one another for their true damage values.
Opting out of PVP
Players can opt out of PvP by joining or creating private servers and restricting access to them. However, even out in general servers, players can simply opt not to fight back to render attacking them pointless.
If you attack someone who doesn't fight back, and kill them, you not only won't receive any caps, you'll also be marked as a Wanted Murderer. While marked, you won't see other players on the map and you'll appear as a big red target on the map to other players. You'll also have a bounty placed on your head, and if someone kills you, that bounty will be taken out of your caps.
It's a pretty severe punishment. And if you're wondering: yes, you can kill your friend if they become a murderer, even if they're in your party.
In order to prevent griefing, all new players are completely immune to PvP interactions until they reach Level 5.
This is done via a passive Buff called Pacifist. Whilst you have this enabled, other players can't damage you and you can't damage them. This gives new players a grace period to gear up and learns the game mechanics, but once you reach level five, you lose the Pacifist buff and become fair game under the rules of the murder system.