Free-for-All, also known as "FFA" or "Deathmatch" in Call of Duty and Call of Duty 2 as well as "Wolfpack of 1" as an April Fool's day joke, is a multiplayer mode featured in every main Call of Duty game, which puts every player against each other.
Do you have to pay money to play Call of Duty? Just like the original, Warzone 2.0 is completely free-to-play for all players and requires no money to play the game.