The value of the chess pieces is a very elementary and essential strategic criterion. In top games even a material difference of a single pawn can be decisive.

 

 

The piece values are calculated in pawn units:

 

 

The program give its positional evaluation in pawn units, always from the point of view of White. If the program is displaying a value of +1.30 this means that it considers the white position to be better by the equivalent of 1.3 pawns. If White is actually a pawn up then the additional 0.3 is the result of positional considerations (mobility, deployment of pieces, king safety, pawn structure, etc.). A display of –3.00 means that White is a piece down – either a bishop or a knight, which are both equivalent to three pawns.