Bratwurst = Finely Chopped Meat Sausage in a literal translation.
I have seen pork, veal, beef, chicken and turkey and nearly as many combinations of those as you can make, described as Bratwurst.
It seems the term is being used in a similar manner to 'British Bangers' which seems to mean many things to many people, in America I have even seen the term 'Bangers' applied to sausages which have no filler, the filler presumably being the reason the sausage was originally given its name due to it's propensity for exploding in the pan.
I think it would be a worthwhile project to collect all common sausage names and prepare a list of definitions for them similar to what has been done at:
http://en.wikipedia.org/wiki/SausageIt would be nice to have a definitive source of sausage descriptions, but I would imagine it would turn into a lot of work to get everybody to agree!
Regards,
Richard