Indexed: Google knows about that page and has it in their index.
Being indexed doesn't mean you rank for anything, but a page that's not indexed can't possibly rank and a page that's indexed under several different URLs (say with and without 'www') will have trouble ranking because its potential authority is being split multiple ways.
Think of the Aesop's fable where the father gives each son in turn a bundle of sticks and asks each son to break it. None can. Then the father unbinds the bundle and gives each son one stick and asks hime to break it, which each son does easily. (http://mythfolklore.net/aesopica/milowinter/13.htm )
When you have multiple URLs for each page, it's like those pages are one thin stick. When you solve the dupe content problems, it's like binding those sticks together.
So you want to look at the indexed pages for your site both to be sure your pages that count *are* indexed AND to be sure that you don't have a lot of junk URLs that should not be getting indexed.