Answer by
CoachC (28)
Games are played to 4, win by 2. Instead of using 0, 1, 2, and 3; tennis uses Love, 15, 30, and 40.
If both players get 40 (aka 3), it's deuce. From deuce, you must win 2 points in a row to take the game; one point gives "advantage". If your opponent wins on your advantage, it's deuce again.