As denotated by the initials on the back of their black and white stripes, we have a [ul][li]Umpire[]Referee[]Field Judge Line Judge[/ul][/li]
But what kind of judge is the BJ?
Back Judge?
Also, what is the difference between the referee and the umpire in (U.S.) football? I know in baseball there is no referee, just an ump, but they seem like they do the same job.
BJ is indeed Back Judge. http://www.nfl.com/news/rulesdigest.html gives descriptions of the various officials’ duties.
BJ is indeed the Back Judge, although outside of football it obviously has other meanings. 
I’m often amazed at the kind of stuff you can find on the Internet. See:
http://football.refs.org/mechanics/
It gives officiating positions for 5, 6, and 7 man crews (presumably, the pros use a 7 man crew) and the responsibilities for each official for various game situations.
Here are your answers 
Taken from http://www.footballusa.com/rules/rules1.htm
(note: Text clipped. It’s all at the linked page, though. -manhattan)
[Edited by manhattan on 11-19-2001 at 05:04 PM]
Hey, Renegade Librarian -
I see that you’re a new arrival (Everyone, show da love for the newcomer!), but the board admin has just put out notices about limiting the pasting of copywrited material. The board is run by a newspaper, which of course has an interest in keeping the integrity of copywrite laws, and does not wish to be seen as hypocritical.
I presume that what you posted is, so maybe just hit the highlights next time, eh? Just a helpful hint.
But thanks for the info anyway.
The umpire is the guy who gets run over by other players a lot since he has to stand in the defensive backfield. Often times, runners use the umpire as an extra blocker.
The NFL has been experimenting with putting the umpire in the offensive backfield (where the referee stands) in order to reduce the number of collisions.
Thanks All.
I think that about covers it
I’m now worried that there are two librarians on this board that know about the dreary vagaries of football rules.
I’m no longer special. 
It doesn’t appear that RenegadeLibrarian violated any copyrights with that post, as the information posetd is not from the official rule book!
I’m going to admit that I’m picky enough to have this bother me:
“pasting of copywrited material.”
That should be “material that has a copyright”.
EJsGirl, it doesn’t matter if it came from the rulebook or not. The point is that someone wrote that passage, and that someone, unless they’ve been dead a long time or gave away/sold the rights to someone else, has a copyright on it. Still a no-no.
Renegade, I’ve removed the copyrighted material from your post. Thank you for the link – it answers any side questions quite well.
But there’s no need to reproduce it here. Folks can just follow the link and get it straight from the source.
No way, man … the next time I have a completely arcane question about sports rules, you’ll be the first guy I think of.
Thank you. I’ve got a world of information on drop kicks in football that I’ve never had a chance to break out.