Final answer:
The 'three-line violation' refers to an indoor soccer rule that is exempted when a keeper throws the ball, allowing the ball to travel over three lines without penalty.
Step-by-step explanation:
The 'three-line violation' mentioned in the question likely refers to a rule in indoor soccer, specifically noted in the context of actions taken by a goalkeeper. In certain leagues, these rules state that a goalkeeper cannot throw or kick the ball in the air over three lines on the soccer field without it touching another player, the ground, or the wall. However, an exemption to this rule exists where if the ball is thrown by the goalkeeper (keeper), the three-line violation does not apply. This is to allow the keeper to restart the game quickly and to support offensive plays.