What is the name of the system used in game analysis that creates a +/- score?

Also what is the Highest/Lowest score possible?  I ask because for the first time I saw a +33.15.

I think this is just referred to as the output of the particular engine's analysis function. It is just a numerical value produced by an algorithm that computationally weighs the pro's and con's of a position. As for the highest/lowest possible score, my guess (as a programmer myself) is that it varies from engine to engine. By the time the score is in the double digits, the game is basically decided anyways so a further positional advantage is just a step along the road to an inevitable win.

I always find it funny if it goes anything over 20.00 , I'm thinking, come on lazy engine, just find a mate already.

Considering you only start with 39 points of material, a +33.15 evaluation is pretty funny, it would be like having a rook and a pawn against the entire opponent army.

Legaly there is probably a way to promote to a bunch of queens each worth 9 points, so I can see it getting really high.

I got an evaluation of over 100.00 when I put this position into Rybka   It's not even a legal position so it doesn't really count...

1...Nf6 2.Nd3
  +-  (99.07)   Depth: 7   00:00:05

1...Nf6 2.Nd3
  +-  (100.75)   Depth: 8   00:00:08

1...Nf6 2.Nd3
  +-  (101.19)   Depth: 9   00:00:29

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This. 

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 the highest is this: #1 (mate in one)

Right.

 

Highest Numerical Value.

I was white in this game (end result was a win for black!)  I had the computer analysis done for this game and at this point in the game it gives the score as -18.22 

Surely a forced mate is possible from there even with best play from white. 

By the way my response to this was King to c1 which the computer analysis described as a blunder.