When a foul occurs the ref can give the fouled team “advantage” where the play can continue to give them a chance to play on from it but if they lose possession or if play stops then the foul will then be called and a set piece can be awarded at that point. The rule is designed to prevent some tactical fouls where you foul a player to prevent a promising attack from properly developing and it also serves to reduce stoppage time and keep the game going.

An example would be if a team is counter attacking and about to have a 3 on 2. If an attacker is fouled then play would stop immediately and the defence gets time to reset, ruining the attack. With advantage the ref can give time for the team to progress their attack to possibly have a goal scoring opportunity. There is a limit on how long an advantage can last but I’m not sure on how long that is exactly