You are looking at an example of a Facebook Tab, being displayed in an iFrame.
Not really that exciting. What is more exciting is that there is a content management system sitting behind the iFrame that let's you control the content of tabs - and ADD MORE TAB PAGES under a single tab.
It's a work in progress, this is a proof on concept.
Once finished, you will be able to add the iFrame application to your page and then get an editable tab to work with yourself.