The "foul line" is a crucial marking in sports like basketball and bowling. In basketball, it is a line that separates the court from the area where players cannot enter during free throws. If a player steps over this line before the ball is released, the shot is considered a violation. In bowling, the foul line is the boundary that bowlers must not cross when delivering the ball. If a bowler steps over this line, the roll does not count, and no pins are scored. This line helps maintain fairness and consistency in the game.