It's usually called a Boston Terrier. Many dog devotees just call them "Boston"s cause its shorter, and because they aren't really terriers. They are "bull terriers" or "bull-and-terriers" deriving their breeding from bulldog breeds and terrier breeds, like staffordshire bull terriers, English bull terriers, and American pit bull terriers.

The Boston terrier was the first purebreed dog to be developed in the United States, is the official state dog breed of Massachusetts, and is the mascot of the Boston University sports teams.

Sorry for the overlong answer to your simple question, but that's what I do!