Passive Mode is a game mode in GTA Online. Passive Mode is similar to Red Dead Redemptions Friendly Free Roam, where the player cannot kill or be killed.
Passive mode is only active while you are on foot (Although you can still get ran over by other players, on the plus side, you can still run them over also). While inside a vehicle, you are able to shoot and get shot at and in the process, get killed. Your vehicle is not immune to Passive Mode. It costs $100 to activate Passive Mode. It is activated through the interaction menu.