This move, ensuring the b3-square for his major pieces, decides the outcome of the game.

White resigned.

Usually in such an open position, the player who is attacking with checks wins. After the natural queen promotion 46...e1=Q+ 47.Kh2, Black has no more checks, and White will launch a decisive attack on his next move.
However, Black found a move White had overlooked (instead of his last move 46.a7-a8=Q, White could have won by 46.Kh1-h2!).

And White resigned, because after 47.Kh2, there follows 47...Ng4+ 48.hxg4 Rh7+ 49.Kg3 e1=Q+ 50.Kf3 fxg4+ 51.Kxg4 Rh4+, mating.

White’s initiative looks very powerful, but Black has a whole extra piece. On 24.Rh8, there follows 24...h5, and there is nothing concrete. But White has available a brilliant tactical resource, involving luring the black queen to the seventh rank, where it can be attacked.

If 25...Qd7 26.Rxd7+ Bxd7, White has many attacking resources, one of which is 27.Bc3 Re8 28.Qd2, with the threats of g2-g4 and Qd2-g5, and a decisive attack on the dark squares.

Winning.

It may appear that Black has chances of a kingside attack, but this is not so. The pawn center d4-e5 solidly protects the squares that Black might want to use to bring up additional resources to the kingside. Even so, White has to hurry, because Black plans to bring his knight via f8 to g6, and then play ...Bd7 and ...Raf8. If he manages this, he will stand very well. But White finds a serious defect in Black’s position, namely the poorly-defended Ng4, and he attacks it:

An open attack on the Ng4. Now, Black is simply lost, because he has to exchange queens.

Or 19...Rg5 20.f4 Nh4+ 21.gxh4 Ne3+ 22.Kf2 Ng4+ 23.Ke1 (23.Kg3+–) 23...Qxh4+ 24.Kd1 Rg6 25.Kc2+–.