What are fox terriers bred for?

for catching rats and to bold underground so that foxes go out of their holes and than they can be hunted.

They were used to get foxes out of their holes so that they could be hunted. And they were also used as pest exterminator.

The Toy Fox Terrier is an American breed descending from the first registered Smooth Fox Terrier, named 'Foiler'. Fox Terriers were bred for fox bolting (chasing foxes out into the open where they...

yep. toy fox terriers are smaller and have fully pricked ears. there are 2 kinds of fox terrier, the smooth, and the wire hair. fox terriers also have a longer muzzle.

I've heard of fox terriers and dachshunds being bred, here: http://www.dogbreedinfo.com/t/toyratdoxie.htm