Please Help

Somebody please explain the terms 'That's bangin' and/or 'that's off the hook.' I've heard this ridiculous proclamations of (what seems to be) joy and/or affection, but perhaps I have misunderstood the meanings of these phrases.

How did they come to be? What do they mean? Why have they become the new 'cool' or 'awesome?' Isn't anything just "cool" anymore, or is it always banging. Where does 'bangin' fit into the following hierarchy of expression:

Good
Better
Best

Cool
Amazing
Awesome

Does bangin' fit in with the 'good,' 'better,' 'best' category? As in "that show was good, but the other one was bangin'. Or does it fit better in the other group?

Please help. I need schooling on the use of these phrases as not to be left behind in the market of expressing my admiration of something/somebody.

Thank you!