Pit bull is the common name for a type of dog descended from bulldogs and terriers. Formal breeds often considered to be of the pit bull type include the American Pit Bull Terrier, American Staffordshire Terrier, American Bully, and Staffordshire Bull Terrier. The American Bulldog is also sometimes included. Mixed-breed dogs which physically resemble these breeds often get labelled as "pit bulls" by shelters. Additionally, the pit bull type is particularly ambiguous as a "breed" encompassing a range of pedigree breeds, informal types and appearances that cannot be reliably identified. Many of these breeds were originally developed as fighting dogs from cross breeding bull-baiting dogs and terriers. After the use of dogs in blood sports was banned, such dogs were used as catch dogs in the United States for semi-wild cattle and hogs, to hunt and drive livestock, and as family companions. Despite dog fighting now being illegal in the United States, it still exists as an underground activity, and pit bulls are a common type used.