Best move scores?

when using programs such as Chessmaster or Rybka or w/e the case may be..... it displays a list of moves/lines/variations each with its own "score" as reported by the computer.

I was wondering how to interpret the Score and Depth of these lists? 

essentially what do those things mean?

IE: Depth 1/7    as opposed to depth 3/7

and

IE: Score -6.23   vs Score 0.34

What do these things mean? an someone give me an indepth exlaination of these things?

Chess engines evaluate positions in 'centipawns'. If the evaluation is negative Black has the advantage and if the evaluation is positive White has the advantage. -6.23 means Black is up by about 6 pawns--in practice he might actually be 6 pawns, or a rook and a pawn, or have an extra queen for a bishop (the value of the pieces is explained here), or maybe he hasn't won such material yet but his position will allow him to win it by force.

Depth indicates how far into a position your chess engine has looked (in half-moves). Beware of comparing depths between different engines or even different versions of engines. A strong engine sees more at "depth=13" than a weaker engine at "depth=15".

From http://www.chessbase.com/workshop2.asp?id=1699

The "Depth" box shows how far ahead Fritz has searched. The first number (before the slash) indicates how far ahead Fritz has looked in a "brute force" search (trying to see every move, and every response, and every response to those responses, etc.). This figure is given in plies. A ply is a half-move (i.e. one move by one player), which is different from what most players normally think of when someone says "x number of moves". For example if someone says "My game lasted forty-five moves", he's talking about 45 moves for each player -- this would actually be ninety plies when expressed in half-moves. So with a twelve ply brute force search (as shown in the display), Fritz is actually looking six moves ahead in the game.

The number after the slash refers to a selective search -- variations resulting from forcing moves like captures and checks. Normally this number is much higher than the brute force value before the slash. I snapped the above graphic just as Fritz was starting its twelfth ply, so the values were the same at that time.

From http://209.85.141.104/search?q=cache:ReBp6qMSPtUJ:rybkaforum.net/cgi-bin/rybkaforum/prevnext.pl%3Ftid%3D5726%3Bdir%3Dprev+Rybka+depth+search&hl=en&ct=clnk&cd=4&gl=us

(*) If Rybka 2.3.2a searches for 3 minutes and reports a depth of 19, while Rybka 3 searches for 3 minutes and reports a depth of 18, does this mean that Rybka 2.3.2a has looked into the position to a greater depth, and therefore must be "seeing" more by looking deeper (even though the breadth may be lesser)?

No, not at all. The depth is just a number Rybka uses to keep track of her search. It does not indicate any breadth vs depth tradeoff or anything else which might be meaningful to the user. All you can say is that depth X+1 for Rybka 3 is deeper than depth X for Rybka 3.

very interesting question... thanks for the answers

ok i think i understand it better now. thx for the explainations. very interesting.

6 years old, but still very helpful :)