The American Staffordshire Terrier is a strong, loyal, and courageous breed of dog. They are intelligent and eager to please, making them great family pets. They are loyal and protective of their owners and can make great guard dogs. They are also very friendly and affectionate with children.
From Wikipedia
The American Staffordshire Terrier, also known as the AmStaff, is a medium-sized, short-coated American dog breed recognized by the American Kennel Club, but not the United Kennel Club, which instead allows American Staffordshire Terriers to be registered under the American Pit Bull Terrier breed.