To win a game, a player needs to get 4 points, and win by at least 2 points.
Having no points is called Love (0). The points in each game are called 15, 30, 40 and game.
The origins of the 15, 30, and 40 scores are believed to be medieval French. It is believed that a clock face was used on court, with a quarter move of the hand to indicate a score of 15, 30, and 45. When the hand moved to 60, the game was over.
When players are tied in a game at 40-40, it is called deuce. The next point gives the winner the advantage but if they lose the next point it returns to deuce. The first player to win two straight points in a deuce situation wins the game.
A set in tennis is the first player to win 6 games and have at least a two game advantage. For instance, 6-4 or 6-3, etc. A player can win a set 7-5 if they win the game when leading 6-5. In some instances a tie-break rule applies. This typically means that when the score reaches 6-6, players will play a tiebreaker to determine the winner of the set. In a tie-break game, the player or doubles team needs to score 7 points and have a two-point advantage to win.
The way the serving works in a tie-break is that the first player serves the first point, player 2 serves for the next two points, player 1 serves for the next two points after that, etc. The winner of the tiebreaker wins the set 7-6.
In the modern game, the winner of a match in tennis is the first player to win three sets for men’s tennis, and the first player to win two sets in the women's game.