The value of close opposition
This is close oposition. When kings face each other like this, whoever has the move loses the oposition. It implies that the white king cannot advance because black has the oposition.
Oposition is important in endgames. If defending king has oposition and maintains it, the oponent cannot advance his pawn and defend it at the same time. It will become a draw one way or another.
It is important if the stronger side can force the other out of opositon.
Oposition is thus an important factor to calculate when you are about the enter the endgame, either as attacker or defender. Here is one of my games.
I think that the best defence is to maintain oposition for black. In this particular situation, it will not help him becase he can be forced out of oposition OR the passed pawn can be abandoned and the white king can advance to free his kingside pawns.