Pit Bull is a genreic term for a group of dogs including the American Pit Bull Terrier, American Staffordshire Terrier, Bull Terrier, American Bulldog. and even more. Technically Pit Bull is a type of dog.
However if your asking what the difference is between a American Pit Bull terrier and a American Staffordshire Terrier it is simply that they were originally bred from the same stock but the ALC wanted to disassociate itself from the cruel dog fighting world so they started their own registry from APBT lines, called them American Staffordshire Terriers and bred for looks and for show. The UKC bred for atheleticism and gameness.....gameness is not to be confused with aggression.
Over the years they remained very close but the looks started to change a bit since the APBT was to look lean and athletic where the Amstaffy's looked a bit rounder (not fat) and shorter....not to be confused with the big headed monsters call American Bullys.
American Staffordshire Terrier: short, stalky BUT conformationally correct.
APBT: leaner and athletic
Americna Bully-a over exagerated unfavored dog that is a fad and of questionable breeding, not to be confused with eitehr of the above dogs with a great history. Unfortunatley its what most of the general public think a pit bull should be
In all of the above breeds most colors are acceptable including the brindle you pictured.
http://www.workingpitbull.com/amstaffpit.htm