Any page that's not indexed by search engines (because of robots.txt, meta noindex or because it's rather new & no one links to it yet, hence SEs haven't discovered it) is a non-indexed page. A page has to be indexed first before it can get any search engine traffic.
Indexed pages means the webpage that has been stored in Search Engine's database and it will be shown in search result page . If you want to check whether your site is indexed by Google or not, then just write "site: domainname" and if you get result, then your site is indexed otherwise it is not indexed by Google. If you want to check them with Yahoo, then you have to check them with siteexplorer.search.yahoo.com
Index page: is a cached by a search engine crawler & it gives pr 0 on the page rank toolbar non-index page: is not a cached by a search engine crawler & it shows n/a on the page rank toolbar