A double team occurs when a defensive player leaves his man to guard a player who is already being guarded. Thus, two players are defending one offensive player. A double team brings an extra pair of hands to deflect passes, block shots or steal the ball.

Sometimes there are players who are playing so well on offence that one defensive player is not enough to stop him, so teams will try to double team that player. This forces the double-teamed player to pass the ball.

This strategy, though leaving one offensive player unguarded, can force the ball into the hands of a weaker player. Many defensive teams would prefer to take their chances with a lesser player making shots, as opposed to the star making plays. John Paxson and Steve Kerr were valuable members of the Chicago Bulls' championship teams because of their ability to make jump shots off passes from a double-teamed Michael Jordan.

Shaq often draws the double team. (Catherine Steenkeste/ NBAE/Getty Images)

Another reason why teams double team is that the guarded player may make a bad pass, leading to a turnover.

When two defensive players double-team an offensive player in certain areas of the court (in the corner or as they come over mid-court), it is called a "trap."

Teams often double team post players (the power forward or centre). Most post players specialize in rebounding and shooting, but not passing, especially not passing out of a double team. Thus, post players may have trouble finding the open teammate when double-teamed.

If the offensive player being double-teamed successfully passes the ball, the defence is at a disadvantage because they only have three players trying to stop four players. The team on defense will try to "rotate out of the double team", meaning they will scramble to recover and match up with all five players again. Sometimes this results in defensive players having to guard offensive players that they normally wouldn't guard.

"Doubling down" is when a guard leaves the perimeter player he is guarding to double-team a low post player. Doubling down can lead to open jump shots for perimeter shooters.