In volleyball, players rotate around the court clockwise whenever the team receives serve. There are several formations commonly used, each having advantages and disadvantages. Offensive formations are usually referenced using two numbers that describe the number of attackers and setters in that order.
4-2 offense
A 4-2 offense uses 4 hitters and two setters. This formation is often used by less experienced teams to avoid confusion on the court. The two setters are positioned opposite each other in the line up so that one is always on the front row and one is always on the back row in each rotation. This results in 2 attackers on the front row at all times. Teams running a 4-2 will rarely set anything other than the basic sets. The benefit of the 4-2 is its simplicity, as it requires less transitioning on the court than other offenses. The drawback of a 4-2 is that it limits offensive options since there are only two (rather than 3) hitters on the front row at all times.
6-2 offense
A 6-2 is similar to a 4-2, but has 6 hitters and 2 setters. This is possible because the setter in the back row is the active setter while the setter in the front row serves as an additional hitter. This formation allows a broader range of sets. This formation is a good option for teams with 2 good setters who are also good hitters. Some young teams also use it so that the player can increase a broad range of skills and not play as only a setter. A 6-2 offense is very common when a team has two setters of equal ability and at a younger age.
5-1 offense
A 5-1 offense uses 5 attackers and 1 setter. Most teams at the highest level use the 5-1 offense. The second setter is replaced by an opposite hitter who is always opposite the setter on the court. This formation allows the setter to dump the ball for half the rotations and have 3 front row attackers to set the ball to on the other three rotations. This system allows the setter to set any possible set. Many coaches prefer this system for more advanced teams, having the one setter serve as team captain. It also helps with consistency since the setter does not change and the hitters can get used to just one setters sets. The main drawback of this offense are that the setter needs to transition from defense to set the ball. This creates situations where the setter has the first contact and someone else has to set the ball.