Some kind of update (patch)

Greetings! I have 3.3.5a World of Warcraft - Wrath of the Lich King expansion pack which works perfectly with every other server, except this one - Warmane. I dunno what has changed since Molten was brought down, but I made an account and tried to log in. And guess what? It started downloading some kind of "patch" or update. I would appreciate if you could tell me what kind of extras is that and why does it happen to be necessary for this server in the latest patch of the Wotlk.
My salutations and good night.

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