UKC and AKC

So I'm still working on my research paper and getting a lot of information, but I have read on here and know that the UKC recognizes the American Pit bull terrier and the Staffordshire bull terrier, while the AKC recognizes the American Staffordshire terrier and the Staffordshire bull terrier.

So what's the difference between the two? (AKC and UKC)