A foul is an illegal action that can be committed by player from one team against a player from the opposing team. Basketball is generally said to be a non-contact game. If contact occurs beyond what is deemed to be reasonable, or if a player thereby obtains an unfair advantage from it, a foul is committed.
There are two types of fouls. The first are called defensive fouls. They occur when the offensive player is being fouled by the defender. Defenders should not block, push, trip, strike or hold the player in possession of the ball. The second ones are the offensive fouls. For example, a player in offence commits a foul when charging into a stationary defender.