CKC means that your puppy is registered through the Canadian Kennel club. I see you are living in the U.S. I take it the puppy was born in Canada for it to be reg CKC.
I have heard good things about the CKC and the UKC over the AKC for showing labs on another board. But i do think they are all wonderful registeries.
I think what any of these kennel clubs represents is a standered of what the breed should be. When breeding they want you to stick within certin guide lines. Making sure the lines are clean and from what i understand they state on the papers if there is a father daughter type breeding. But i'm not really sure what you are asking. You can go on the CKC and the AKC sites and read up on whatever you would like to know..

www.ckc.ca
www.akc.org