Authority sites - what are they?

This SEO term is rather an SEO theory IMHO. Even though I don't trust every word what Matt Cutts says, I think he mentioned that Google doesn't treat in a special way toward .edu sites, for exmaple.

Having said that, I tend to agree that certain sites are recognized little differently from other average sites as many other webmasters think so.

But what are the factors that Google supposedly decides a website to be more authoritive than others?

Possible reasons:

Domain age
PR
Number of backlinks
Indexed pages
Often-updated contents

Besides the obvious ones above, what would you add to the list?

 

Well, I've found two spammy authority sites, so maybe add that to your Google quality sites list.

 

Good question.
Personally I think they exist.

 

Age is a big factor

 

my example of authority sites is botw.org