writer (n.) one that writes
author (n.) one that originates or creates
The distinction is small but important. Writing is a technical discipline, not an art form. Anyone with enough diligence and practice can put words together and construct logical sentences. She can even get pretty good at what I call the microlevel of writing: strong verbs, lack of dangling participles, careful attention to word repeats and adverb avoidance and that kind of thing. The sorts of things that authors generally get smacked around about at FLEs.
An author, on the other hand, creates, births a whole story -- sometimes a whole world -- from flat nothing. Think about that for a second. In many respects, an author is a god, or at least a demigod, a mystical creature who can play a reader's emotions, make social arguments, change the real world... all based on some words.
I'm a damn fine writer who aspires to be an author.