"Today we're going back to basics. We'll be answering the question: What is a website?...Okay, not exactly. But we will be looking into what a "website" means in the context of Webmaster Tools, what kind of sites you can add to your Webmaster Tools account, and what data you can get from different types of sites.".

http://googlewebmastercentral.blogspot.com/2008/10/wheres-my-data.html