The score represented by 30-15 in tennis refers to the game score when one player has won two points and the other has won one point. Tennis uses a unique scoring system where points progress in a sequence: 0, 15, 30, 40, followed by winning the game if a player reaches 40 and has at least a two-point advantage. This scoring system can sometimes be confusing for newcomers but adds to the nuance of the game.