Some of the most competitive sets in tennis come down to a tiebreaker: an extra game in which one player must score at least seven points to win.
How do you reach this point? It's pretty simple: a tiebreak situation arises when both sides have won six games in a set. Typically, a player would need to win at least six games, while holding a two-game advantage, to take the set - but those rules no longer apply when the score is tied 6-6. Instead, the opponents play one more game, and whoever wins it, wins the set. The final score will then be seven games to six, and that's sufficient to win when a tiebreak is involved.
To kick off the tiebreak, the player whose turn it is to serve begins by serving one point. Their opponent then serves one point, and from then on until the game ends, the players alternate serving two consecutive points each. Every six points, the players switch ends of the court, which helps mitigate any environmental advantages, such as wind or sunlight.
A player must reach seven points minimum and have a two-point advantage over their opponent to win the tiebreak. So, if one player has six points and one has five, and the player with the advantage scores the next point, they win the game and the set (and possibly even the match), because they met both conditions for winning the tiebreak. But if the players were tied at six points, it wouldn't matter who won the next point because no one could achieve a two-point advantage; instead, they would keep playing until someone managed to pull away.