A point is scored when the ball contacts the floor within the court boundaries or when an error is made: when the ball strikes one team's side of the court, the other team gains a point; and when an error is made, the team that did not make the error is awarded a point, in either case paying no regard to whether they served the ball or not. If any part of the ball hits the line, the ball is counted as in the court. The team that won the point serves for the next point. If the team that won the point served in the previous point, the same player serves again. If the team that won the point did not serve the previous point, the players of the team acquiring the serve rotate their position on the court in a clockwise manner. The game continues, with the first team to score 25 points by a two-point margin awarded the set. Matches are best-of-five sets and the fifth set, if necessary, is usually played to 15 points. (Scoring differs between leagues, tournaments, and levels; high schools sometimes play best-of-three to 25; in the NCAA matches are played best-of-five to 25 as of the 2008 season.)
Before 1999, points could be scored only when a team had the serve (side-out scoring) and all sets went up to only 15 points. The FIVB changed the rules in 1999 (with the changes being compulsory in 2000) to use the current scoring system (formerly known as rally point system), primarily to make the length of the match more predictable and to make the game more spectator- and television-friendly.
The final year of side-out scoring at the NCAA Division I Women's Volleyball Championship was 2000. Rally point scoring debuted in 2001, and games were played to 30 points through 2007. For the 2008 season, games were renamed "sets" and reduced to 25 points to win. Most high schools in the U.S. changed to rally scoring in 2003, and several states implemented it the previous year on an experimental basis.
The libero player was introduced internationally in 1998, and made its debut for NCAA competition in 2002. The libero is a player specialized in defensive skills: the libero must wear a contrasting jersey color from their teammates and cannot block or attack the ball when it is entirely above net height. When the ball is not in play, the libero can replace any back-row player, without prior notice to the officials. This replacement does not count against the substitution limit each team is allowed per set, although the libero may be replaced only by the player whom he or she replaced. Most U.S. high schools added the libero position from 2003 to 2005.
The modern-day libero often takes on the role of a second setter. When the setter digs the ball, the libero is typically responsible for the second ball and sets to the front row attacker. The libero may function as a setter only under certain restrictions. To make an overhand set, the libero must be standing behind (and not stepping on) the 3-meter line; otherwise, the ball cannot be attacked above the net in front of the 3-meter line. An underhand pass is allowed from any part of the court.
The libero is, generally, the most skilled defensive player on the team. There is also a libero tracking sheet, where the referees or officiating team must keep track of whom the libero subs in and out for. Under FIVB rules, two liberos are designated at the beginning of the play, only one of whom can be on the court at any time.
Furthermore, a libero is not allowed to serve, according to international rules. NCAA rules for both men and women differ on this point; a 2004 rule change allows the libero to serve, but only in a specific rotation. That is, the libero can only serve for one person, not for all of the people for whom he or she goes in. That rule change was also applied to high school and junior high play soon after.