EX: http://www.google.com/search?hl=en&q=nasa NASA is an authority site... Search for any other ordinary site you would not get those special site links and sitesearch box....
Google calls those special links sitelinks. It doesn't necessarily mean you have an Authority site -- according to Google: But NASA is definitely an Authority Site.
Authority sites have an edge over normal sites. They have quality content that's appealing ..this is what we call authority blog in blog lingo...
1. authority website is a website can independent exist without any other website. 2. authority website normal rank 1st on the site name or keyword 3. normal PR5+ 4. ....
I have to disagree with you on the PR 5 as i used to manage two websites with PR 2 and have the site links in google... It's all about having good content and good inner linking structure.
put in simple words a back link from a really reputed page ... the more you get the better for you.. tell me when u get the first one