It is about ending up neutral.
You can't live a modern life without polluting. THe point is to try and offset that pollution.
I drop a stone in the water and it rises. I take one back out and the level goes back. It isn't that simple in a very coomplex system, but that is the concept.
No, I get that. You try to offset one thing with another. If Dave Matthews kills a child yet pays to have another child flown to a place where he can get a life-saving transplant, does that mean he's "even"?
Some might say just don't pollute the enviornment with your tour bus and generators,etc. I guess his Earth Mother doesn't beat out tour dates in Chigago and Tulsa...