Reading Chess Analysis

Ok, I'm relatively new to chess and am getting into studying openings and tactics.  I have a couple of open source analysis tools on my tablet and am wondering how to read them.  I set up a position and then have "Stockfish" as well as "Critter" analyze them.  They read out a list of recommended moves as well as a rating something like +/- (4.52).  What does the +/- (4.52) mean and how do you interpret it?  Thanks so much for the help.

the number means they view the position as being approx 4.52 pawns up. look on the wiki for chess annotations to find other symbol meanings,

Does the negative number mean white is up and a positive number would indicate black is up?

No, positive is white up, and negative is black up.

Do you have a link to that wiki by any change? Can't really find where that is.  Thanks.

other symbol meanings can be found here...

http://www.chessstrategiesblog.com/chess-notation/

That also can depend on the chess engine.  I understand some engines use a positive evaluation meaning the current player (white or black) is up, and negative meaning the current player is down.

http://en.wikipedia.org/wiki/Chess_annotation_symbols

Thanks for the comments everyone.  Found them very helpful...

Is this thing (game analysis) usefull for beginners? Or it is too early for them  to analyse their game?

Everyone should analyze their games. Engine analysis isn't as useful as figuring out why you actually went wrong though.

So a player should replay every move of the game and think what could be done differently?

if you can get a better player that you, or even a titled player to analyze your games, that is also very good

I don't know what the recommended path is but, yes, I find it VERY helpful to replay my games.  With each move, the engine analysis assesses the strength of the move and if it changed the swing of the game at all.  I can then assess if there were any better moves.  I'm also reading several books so those, along with the engine analysis, are helping a LOT!!

also i want to learn about chess analysis. i have a pgn viewer on my android phone. while studying a puzzle, i activated the analyse option and it showed
[56] m2 Bc6 Qg1 Ra8+
d: 56 O: t: 0.24 n: 8248 nps: 3380

what all these mean ?