In my defense...since I do generally try and make my posts as helpful as possible...
CL and CR are standard d20 terms. I could say "Challenge Rating" and "Character Level," but it would be superfluous if you didn't already know what I was talking about....and CL and CR are the standard way of referring to such gaming concepts in the rulebooks themselves. In fact, many gamers only know them by their short names, so there's a good chance that if I actually typed out Challenge Rating I would be confusing more people.
So...it's really not a "interw3bz" shorthand, poor linguistics, or any other such thing. They are concepts and terms that are well-established in the gaming community. I'm really sorry if I confused anyone. But that is what Google is for, just like when people sometimes use words that I don't know.