A very warm welcome from all of us here at onering - its a fun forum, and so friendly you wouldn't believe it. Thats now three girls I know that are into LotR! You, Shieldmaiden and my better half who has an unhealthy obsession with Haldir and his wood elves.
In answer to your question, Terrain is the bits of scenery on the table that turn it into a miniature tabletop world. Things like trees and buildings. We got some pillars, Balins tomb and a doorway with Mines of Moria - now that The Hobbit is due to replace it I would expect some trees or something fun in the box set.
Great time to discover the hobby, The Hobbit release will bring an ideal starter set for anybody looking to get into gaming, its bound to include Gandalf and the Dwarves as well as a few bad guys. Alternatively, alot of us here do just love to pick up a good looking model and .. well, paint it!
So, go ahead, dive in and grab whatever models you like - paint away, relax and enjoy! But do let us know what you get up to as we're all interested in each other's evil exploits.
Big hints to round of: Other than gaming and painting, there is some great backstory in some of the extra sourcebooks Games Workshop sell, and the "tomes of wisdom" right here on the site have a ton of awesome articles to check out.
Also, never buy your models from Games Workshop! Almost everyone on here buys from independent stockists like myself as its usually about 25% cheaper and helps out the friendly local gaming stores
(FLGS), and GW staff have (rather sadly) turned from hobby enthusiasts to sales driven monsters in a large number of stores.
If you're keen to know more, wait until later this week and pick up a copy of White Dwarf magazine from somewhere, it is bound to be packed with info on the new Hobbit release as well as a neat little insight into what else Games Workshop produces.
Hope that helps!