Just like American football, soccer and some other sports, volleyball teams have the opportunity to have a player who specializes on defense. This player is called a libero. This player is usually quick, may be shorter than many of the other players and has honed his or her defensive skills to a fine point.
For the libero, life is all about defending against spikes and helping control the ball for an eventual attack. While the libero may have dreams of scoring a point, this rarely happens due to the rules designed specifically for this specialized player.
In order to use a libero, a team must declare that person as such before a tournament begins. Once declared, that libero can substitute freely for any other volleyball player, but must stay on the back line. Liberos cannot block, attempt to block, or serve. Further, volleyball players on the front line cannot attack from a point higher than the net if receiving a fingertip pass from a libero who moves to the front zone during a rally.
A libero, if on the team and in the game, should be relatively easy to spot. He or she is required to wear a different color uniform than that of the rest of the team. This is not only to help officials clearly identify the player, but also to remind teammates they cannot attack off a libero's fingertip pass, if the libero is in the front zone.
The advantage of a libero is that he or she is not subject to the normal substitution rules by which other players must abide. Typically, only six substitutions are allowed per set and once a player leaves the game, he or she can come back in once, but then must stay in the rest of the set. None of these rules apply to liberos. This gives teams who have an exceptionally talented defensive player a little bit of an advantage, especially if their more offensive-minded players are not as skilled in defending.