What is the point of this engine-recommended h5??

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This position was reached in a game I played today:


 It looks to me like the best move for black is Nxc3, forcing white to mess up their kingside pawn structure and trading equal material from a material advantage.

But Stockfish recommends h5.   By over 25 cp.

What?

Can anyone explain the point of this move to me?  What on Earth is it "thinking"??

Chess_Player_lol

the computer is giving me Bd6 and Be7 with h5 as the third choice. it probably just likes gaining space and it has the time to do that due to the material advantage