Beer Barrel Poker is a popular card game that involves tapping a beer barrel to determine the order of play. The term 'TAP' is used to describe the action of striking the barrel with a mallet or other object to create a sound. The game is usually played with four players, each taking turns tapping the barrel and then dealing out cards. The player who taps the barrel first is the dealer and the other players must follow suit. The goal of the game is to have the best hand at the end of the round.