The ball is out of play when: it has wholly crossed the goal line or touch line (outside edge of line) whether on the ground or in the air; and, play has been stopped by the referee.
If football uprights are being used as soccer goals, the ball is also out of bounds when it strikes a part of the football uprights that are not part of a goalpost or crossbar.
The ball is in play at all other times, including when: it rebounds from a goalpost, crossbar or corner flagpost and remains in play; or; it rebounds from either the referee or an assistant referee when they are on the field of play.