What do the computer evaluation numbers mean (like +2.25)?
Chess engines (computer programs) use a standard notation to indicate who is better off (White or Black) in a given position.
A positive ("+") number means that White's position is better
A negative ("-") means things look better for Black.
The number itself is based on the 'value' of the different chess pieces:
1 = a pawn
3 = a Knight or Bishop
5 = a Rook
9 = a Queen
However, the evaluation is not just about material currently on the board. The engine analysis also looks ahead, factoring in positional aspects and tactical possibilities.
So, if the evaluation is +2.25, it means that white is ahead by 2.25 pawns (or "points").
White might not actually be up any pawns at all, but might have such a good position that the engine sees it as the same advantage as if they had two extra pawns.
Likewise, if the evaluation is -3.00, then Black is ahead, and Black's advantage is about the same as having an extra Bishop or Knight!
Sometimes, near the end of the game, you might see an evaluation like +M2: bad news if you're playing Black... This means White can force checkmate in two moves!
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