What is a swimbait exactly?Who makes um?Thanks alot

That's like asking what's a rod and who makes um?  Your question is a very broad one.  Use the search feature to find recent posts regarding swimbaits and also check out the articles on the front page, read them and then come back and ask any questions you might have.

People could write a novel on the question you just asked.

A broad answer for you would be - A bait that looks and swims like a fish.  Almost all bait manufactures make some sort of swimbait.

http://www.mattlures.com/

Check this link out.  this should help you.

The Fishing Tips section on the Mattlures site mentions use of the swimbaits for large/trophy fish.  Can one use these if they were fishing for less than trophy sized, or would it be overkill?

Big baits that catch big fish and attract lots of monkeys.

You catch fewer small fish with the big baits, but you do still get a brave one every once in a while,lol