You have the Firelands Raid which contains 7 or 8 bosses and is accessible through the raid portal entrance at the Sulfuron Spire you can check it out in 4.1 if you go there but it will be blocked by a gate not allowing you access until 4.2 is released.
You also have the Firelands questing zone which is available in 4.2, which you gain access to via a portal in Hyjal after meeting some questing and daily questing requirements.
So to answer you question it is both a raid and a new zone.
The raid portal pretty much takes you directly to Rag's doorstep, the questing portal just takes you to their neighborhood. Both though are in the Firelands.
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Deraxacus - Area 52 (US) (Horde)