Suppose there was a wall or other obstacle between you and the destination. Then you might have to go "back" to find a way around. Vanilla A* can't "know" wheth

Suppose there was a wall or other obstacle between you and the destination. Then you might have to go "back" to find a way around. Vanilla A* can't "know" whether this is the case, so it searches outwards in all directions, using the heuristic to weight the search towards paths that are getting us closer to the destination.