When any player of the attacking team crosses the blue line before the puck, the ref raises her arm.
If an offending player does not touch the puck and her goes back into the neutral zone (one skate touching the line) and all of her teammates are also in the neutral zone with at least one skate touching the blue line or in the neutral zone then the delayed off-side is waved off (the ref’s arm will drop to his side) and the attacking players can now go after the puck that is in the attacking zone.
Each player must wait until all of her other teammates also have at least one skate on the blue line or in the neutral zone before being allowed to chase after the puck.
So when you hear everyone yelling “OFF OFF OFF“, check your position to see if you are off sides!