Tennis scoring looks like a code: 15, 30, 40, love, deuce, advantage. It is actually a simple ladder — points build into games, games into sets, sets into matches.
Points: 15, 30, 40, game
Win a rally, get a point. The server's score is always called first: 15–0, 30–15, 40–30. Win four points and you win the game — unless both players reach three points (40–40), which is called deuce.
Deuce and advantage
From deuce, you must win two points in a row. Win one and you have 'advantage'; win the next and the game is yours. Lose it and you are back to deuce. Long deuce games are where matches are really decided.
Games, sets, matches
First to 6 games wins the set (with a 2-game margin, or a tiebreak at 6–6). Men play best-of-5 sets at Grand Slams, best-of-3 everywhere else; women play best-of-3. 'Love' simply means zero — from the French l'oeuf, the egg.
Tiebreaks
At 6–6, a tiebreak decides the set: first to 7 points (2 clear), with points counted 1, 2, 3… and players swapping serves every two points. It is tennis's penalty shootout — pure nerve.