When a score is tied you can say 15-15 or 15 all. Now one player must win two points in succession to win the game. The person who wins the next point has the advantage. In if the server won the point, and Advantage Out if the person receiving the serve won the point. Regardless of who wins the first game the receiver becomes the server for the second game, and so on alternately after each game.
Players change sides or after the first game and every other game after that.
In other words, after every odd numbered game you change sides. A set in tennis is a least 6 games. The person who wins the set must win 6 games and be at least two games ahead of the opponent. A match in tennis is determined by the best two out of three sets. When two players play as partners against two others, the game is called Doubles.