Many people are confused about all the canine registries around now.  I have a list here that might help you understand.

First, dog registries keep records about dogs.  A registry will record information such as the dog's name, breed, color, who owns it.   Information about each dog is tracked with a unique registration number.   These records often include such things as a pedigree, any titles earned,  sometimes DNA profiles -  and are collectively known as a dog's 'papers'.

AKC - American Kennel Club    This is the primary, most recognized registery in the United States, offering the most breeder / owner information of any kennel club.  Each breed recognized by AKC has a 'parent club' that focuses on that one breed and represents the interests of that breed with the AKC.  The American Cavalier King Charles Spaniel Club is the parent club for Cavaliers.

UKC - United Kennel Club   This is the 2nd oldest registery in the United States, a pioneer in DNA testing to verify pedigrees.  The UKC has a club-wide code of ethics which is printed on all registration forms and helps discourage retail sales of puppies as well as other responsible guidelines.

I personally feel the AKC & the UKC are the most reputable registeries in the USA at this time.   Most of my dogs are registered with both of these organizations.

UKC - Universal Kennel Club    This organization has a strong emphasis on classifieds and Rat Terriers.  Not a registery I recommend.

CKC - Canadian Kennel Club    The Canadian equivalent to our AKC - an excellent registery

CKC - Continental Kennel Club    An 'Open Registery' - will register mixed breeds for the purpose of breeding them.  Will recognize more than one standard per breed.  Not a registery I recommend.

WKC - World Kennel Club    Classifieds message board - infamous in some internet dog circles - run by a singe person, no listing of recognized breeds.

FCI - Federation Cynologique Internationale    The kennel club for the rest of the world -- an organization that keeps breed standards and related records for national kennel clubs in other countries.

FIC - Federation of International Canines     a 'bogus' organization - mostly advertising with no mention of health screenings or other responsible breeder information. 

ARBA - American Rare Breeds Association     Recognizes rare breeds not recognized by AKC.  Usually foreign breeds, recognized by FCI, but not AKC.  Main source of competitions for the rare breeds.

There are also breed-specific registeries,  which handle information about a single breed, usually for breeds not registered with the AKC and/or the UKC -

CKCSC, USA - the Cavalier King Charles Spaniel Club, USA    This is the organization that was formed when Cavaliers were first being imported to the US.  They kept a registery of all dogs here, puppies born, and other information originally with the intent of becoming recognized by the AKC at some point.   Before being recognized by AKC, this organization changed its ideas and voted to not affiliate with the AKC.  A group of 12 people who knew quite a lot about the Cavalier came together and formed the ACKCSC, which is the parent club with the AKC for all Cavaliers now.   The CKCSC, USA has continued to operate as a separate, if parallel, registery / organization.   I personally feel this organization does much to divide and maintain conflict within the breed - instead of putting the welfare of the breed as their primary focus.  I do not register my dogs with CKCSC, USA.