Advantage After a Restart Taken Wrongly
A throw-in taken from the wrong place, a free kick struck while the ball was still rolling: if the other team benefits, the referee can now wave play on instead of calling it back.
A restart taken incorrectly was retaken, whatever happened next.
A restart taken incorrectly with the ball in play may be left alone if the opposing team benefits. Otherwise it is still retaken.
What changed
Law 5's advantage clause used to name one trigger, an offence. It now names two: an offence, or a restart incorrectly taken with the ball in play. The referee allows play to continue where the opposing team will benefit, and penalises the offence or orders the retake if the advantage does not ensue at that time or within a few seconds.
Why it matters
This is the change most likely to look like a mistake the first time you see it given. A foul throw that lands at an opponent's feet has always been called back, and calling it back rewards the team that took it wrongly. The new wording lets the referee leave the ball with the side that did nothing wrong. The test is not whether the restart was legal, it is whether the other team is better off than a retake would leave them.
Scenarios
Foul throw straight to an opponent
A player takes a throw-in with one foot clearly off the ground, and the ball goes straight to an opponent who runs with it.
Free kick struck while the ball is still rolling
A free kick is played quickly while the ball is still moving, and the kicking team keeps possession and works an opening.