Tennis Scoring Formats

If Player A wins set 1 and set 2, the match is over. But if Player A wins set 1 and loses set 2, the match would be decided by who wins the 3rd set.

For example:   

Stefanos Tsitsipas beat Roger Federer 6-4, 6-3  

or  

Venus Williams beat Serena Williams 6-3, 4-6, 6-2

All sets are 'tie break' sets which simply means if a set reaches 6-6 in games, a tie break is played.

(see below for more info).   

For example:   Rafael Nadal  beat Novak Djokovic 6-3, 7-6 (7-5)

In League matches, when any set reaches 6 games all, a tie break is played.   

• The player whose turn it would have been to serve in the next game, starts the tie break, serving just ONCE to the deuce court (bottom right to top left, from above). 
• The opponent then serves the next TWO points, starting with a serve to the ad court (top right to bottom left, from above).  
• Points are numbered 1, 2, 3 etc. rather than 15, 30, 40, Deuce.  
• From the 2nd point, each player serves for the next 2 points. The tiebreak is over when one player reaches 7 points, provided they are 2 clear points ahead of their opponent. If the score gets to 6-6 in a tie break, a player must have a two point advantage to win the tie break.  
• A tie break score could be 7-5, or 8-6, or 9-7.   
• After every 6 points played, players change ends, i.e. at 3-3 or 6-6. The players also change ends at the end of the tie break to begin the next set.  
• The player who served first in the tie break, RECEIVES at the beginning of the next set (assuming there is one).