The term lasting advantage (or gained an advantageThe term gained an advantage or lasting advantage is typically used when a driver leaves the track and rejoins with... There's more...) is typically used when a driverOK, so we all know what the driver is, right. I've always liked the description that F1 drivers are like... There's more... leaves the track and rejoins with an advantage over his nearest rival, that he would not have achieved if he had not left the track.
In this instance, the driver deemed to have gained an advantage is required to give the position back. Teams are expected to make this decision and give the direction to the driver, however, if they don’t the stewards will.