Nine-ball is a billiard variation where players only use the balls numbered one through nine. In a 9-ball rack, you rack the balls in a diamond pattern, with the one ball at the front of the rack and nine ball in the center. The object of nine-ball is to hit the balls in ascending numerical order, starting with the one ball. You don’t need to pocket the lowest-numbered ball first, but you must hit the lowest-numbered ball on the table before pocketing it or any other ball.

Straight pool is a called-shot game. The object of straight pool is to shoot any ball into a pocket; you don’t have to aim for a particular set of balls or shoot the balls in any particular order. Straight pool players designate a score ahead of time; typically 100; and the winner is the first person to reach that score.
In straight pool, every ball sunk on a called shot counts as one point. Under called-shot rules, you can only designate one ball per shot; even if multiple balls are pocketed during a shot, all balls that are not the object of the called shot are returned to the table and the shot only counts as a single point. Because scores are typically 100 or 150, straight pool, or continuous pool, involves several consecutive games.

Eight-ball is a game where each player must pocket one set of balls; either the solid balls numbered 1 through 7, or the striped balls numbered 9 through 15. Like straight pool, the 8-ball billiard game is another called-shot game. Players must announce the shot they intend to make before striking the cue ball. If they fail to make the shot, their turn is over and play reverts to the opponent. The object of eight-ball is to pocket every ball in the player’s set, and then pocket the eight ball on a legal shot.

Cutthroat is a pool game for three players. In cutthroat, each player gets five balls; either group 1 through 5, 6 through 10 or 11 through 15. The object of the game is to sink your opponents’ balls while keeping your balls on the table. Whenever an opponent scratches, you can return your ball to the table, so the game isn’t over if all your balls get pocketed. When you successfully sink all of your opponents’ balls and have at least one of your own left standing, you win.