An offensive strategy in which the team tries to move the ball into scoring position as quickly as possible (either by passing or by dribbling) in order to get a man advantage on offense.
A fast break usually occurs after a terrific defensive stop or a forced turnover, allowing the team to obtain possession and move the ball down quickly before the opposing team can set everyone up on defense.
A fast break usually involves one or more players who have an advantage in numbers as they move the ball down the court towards the basket. Most fast breaks are the result of a turnover by the opposing team, usually created by way of a steal or a blocked shot. Often lineups with smaller, quicker players are more likely to employ the fast break, making use of their speed and ability to steal the basketball to create easy baskets in transition. There is no real efficient way to defend against a fast break as the circumstances usually dictate that the offense has the advantage-some players will prevent fast break scoring by fouling but must be careful as sometimes points and possession can be awarded to the team on the fast break if it is determined that the ball handler had a "clear path" to the basket.
Fast breaks can also occur if the team on defense is particularly lazy in transition, meaning that the team with possession doesn't necessarily have an advantage in numbers or any breakaway speed. This often involves the ball handler passing to a player who cuts behind the defense in front of the basket for an easy layup.