If it weren't for that glorious third eyebrow on his forehead, I wouldn't have deemed him a handsome man.
Explanation:
A complex sentence contains a subordinate clause! In the sentence I have written for you above, <em>if it weren't for that glorious third eyebrow on his forehead </em>is the subordinate clause! It added some info to the whole sentence, but cannot stand as a complete one on its own.
It is used in the beginning so that the story makes sense to the reader. so for example...trying to put information out there while trying to get the reader hooked