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At first glance, it looks like White has traded down into a drawn opposite-colored bishops ending. Sure, White does have a couple of things to worry about in his isolated in d-pawn and Black's queenside majority, but they don't look too hard to defend.

In these OCB endings, the superior sides needs to set up threats as widely separated as possible. So Kholmov opens up a third front on the kingside!

First he makes sure his pawns are on light-colored squares. This protects them from White's bishop, but also has a subtler effect. When Black begins the softening up process with 38...Bf1, White's kingside pawns end up on dark squares, meaning his kingside light squares are vulnerable to penetration by Black's king.