If you use the Analysis feature of the site, it gives you a full variation for each candidate move (not just its score). Playing through these full variations will help to explain why Stockfish likes certain moves. In your position, the engine chooses Pb3 to allow the WB to retreat to b2, especially against ...Ne4, i.e. White doesn't want to exchange the minor pieces, and wants to keep the B on the long diagonal.
I think the only thing 1.b3 does is give your bishop and escape square on b2, after black plays 1...Ne4. But honestly, the bishop pair is not a decisive advantage here.
Thanks, you're right. Without playing b3 preemptively the only way to avoid the knight vs bishop trade on c3 is to play Bb4, which is answered by ...c5, forcing the bishop to the useless a3 square. And otherwise I have to move the queen or rook to avoid doubling my pawns on the c-file. Overall a bad position.
I know about the analysis tool, but it only shows the "good" lines, so it's not as easy to know what lines the AI is *avoiding*. Especially since it often delays playing the decisive moves like Ne4 here.
Because the AI pinned my knight, I played Bd2 in response, and the AI exchanged their bishop for my knight without doubling my pawns, God knows why. Level 10 btw.
Bishop took back on c3.
I was running Stockfish in the background to compare my play with the AI's, it's good training.
In this position I was planning to play g3 (to contest the open a8-h1 diagonal with a discovered knight attack) or e3 -> Be2 and castle kingside.
Stockfish (and also the chess.com advice) rated my two ideas as neutral to slightly positive, but advised me to play b3. They rated b3 as a 0.5 pawn gain.
I just don't get it. What's so good about this move? I know, the c4 pawn is undefended, but I have lots of ways to defend it. I can answer ...Ba6 with b3, making the bishop useless on that square and winning a tempo.
Can someone explain? Is there some sort of attack on my c-pawn I missed, are AI's just overprotective of their pieces and can't stand them being undefended, or is it something else entirely?
Thanks.