
Hi Lesley
it's an American registration system, separate to the main body we know as the American Kennel Club however many dogs are registered under both and shown at events run by both. So a dog could be an AKC & UKC Ch for example. (UKC is United Kennel Club)
They hold their events completely separately from one another and some of the rules are different too - in my breed outside attraction for example is allowed at UKC events when the dog has been judged and is being critiqued. Doubtless a lot more to it than that of course but one sample of differences :)
ETA : Here is a
LINK to the UKC. If you read also the
AKC site you'll note the conditions under which certain breeds registered with the UKC can be registered with the AKC (some breeds are not recognised by both registries)