What does a break mean in tennis?

The server starts each game with an edge, so holding serve is the default and a break is the event. Commentators track who is "up a break": ahead by one game against serve.

Breaking back means winning the next return game straight after being broken, which levels the set again.

Questions

What does up a break mean?

One player has won one more of the opponent's service games than they've lost of their own.

What is breaking back?

Winning a return game right after losing your own serve, which cancels the break.

Sources

  • ITF Rules of Tennis