So there are different sub-forums used for different functions, such as traveling to people's towns leisurely, buying things with in-game bells (IGB) or Bell Tree Bells (TBT, the site currency), the Animal Crossing forum that talks specifically about the game, the Nintendo treehouse that talks about Nintendo games in general, Gamer's Lounge that talks about videogames in general, or the Cafe and the Basement, which are basically for discussions that don't have anything to do with videogames.
Currently the value of 1 TBT is 200,000 IGB.
TBT can be used to buy things like villagers, collectibles, rare in-game items, and anything else that's rather difficult to obtain in the game and on the site.
You can earn TBT by selling collectibles, villagers, items, artwork (in the museum sub-forum), or simply by making a post.
If you lurk around on some threads, you'll understand this site a lot better. It's not super difficult to understand once you learn what it's all about.
If you have any more questions you can always ask me. I pretty much know anything about everything on here.