What does deuce mean in tennis?

The International Tennis Federation states that "deuce" is the score when both players have won three points each in a game. The next player to score a point will have "advantage." If the player having advantage wins the next point, then they are awarded the game.

If the opposing player wins the next point, then the score goes back to deuce. The standard scoring for a game in tennis is 15 for the first point, 30 for the second point, 40 for the third point and "game" for the fourth point. The first player to win six games is awarded the set. Most matches are won by winning two of the three sets played.