The only generalization I would make about the breed is that each makes me laugh each day. All be it, in their own unique way.
With that in mind, here is an abridged version of how Wikipedia describes the Bull Terrier:
Appearance: The Bull Terrier's most recognizable feature is its head, described as 'egg-shaped head." The profile curves gently downwards from the top of the skull to the tip of the nose. The body is full and round, with strong, muscular shoulders.
Colors: They are either white, red, fawn, black, brindle, or a combination of these.
Temperament: Their personality is described as courageous, full of spirit, with a fun-loving attitude, a children-loving dog and a perfect family member. A 2008 study in Germany did not find that Bull Terriers had any significant temperament difference from Golden Retrievers in overall "temperament researches."