It's an interactive map of Ulduar (same graphics as the in-game map), and if you click on any of the boss icons, it pops up a little paragraph about the boss. For instance, did you know that Auriaya is Ulduar's archivist? Makes sense - librarians love cats. Also, apparently Kologarn was created by Ignis. I guess Iggy must have been a big Monty Python fan.
I think this is a neat way to learn a little more about the story behind the bosses. I hope they continue doing this for raids to come.