What is the scoring system in volleyball called?

It depends on what level you are playing at. I play on my high school team and we use rally score. We go up to 25 points and you have to be at least two points ahead to win the game. For example if the score was 25-24 the game would not be over the winning team would have to get one more point to win the game.

Rally scoring is when you win the volley [the ball hits the floor on the other teams side or out on your side etc.] you get a point whether or not your team served the ball. In 8th grade we used the original scoring way. We only went to 15 points then but you still had to win by two points. The original scoring is when you have to serve the ball and win the volley in order to get a point.