When it comes to tennis there is more to betting then on just the outcome of the game

Match betting
Bet on the Outcome of an individual match

Correct Set betting
It is common to bet on the number of sets required to win the match

Game by Game betting
The objective of Game by Game betting is to correctly predict the points score per game.

There are eight possible results for a game:
Server wins to love
Server wins to 15
Server wins to 30
Server wins to deuce
Receiver wins to love
Receiver wins to 15
Receiver wins to 30
Receiver wins to deuce

Handicap betting
Handicap betting is normal available at most bookmakers for tennis matches.

Total games
Bet on whether the total number of games in a match will be over or under a particular number, e.g. 21 or less/ 22 or over. This is similar to spreadbetting