It sounds like : "I can pollute the enviornment and buy some 'credits' and that means I'm actually cleaning the enviornment."
I don't quite follow.
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.