this is a re-flippin'-diculous question... Sorry, I just assume people should know stuff like this, and it's wrong of me ^_^ not very nicelike. Anyway, the main jist of Animal Crossing is that you travel to a new town to start a new life. There you get a house, which you have to pay off to the local storeowner, everyone's favorite raccoon Tom Nook. You can pay off debts by doing favors for neighbors (NPC animals that say the darndest things), fishing, catching bugs, and digging up fossils (you can also donate these items to the museum and build up the musuem's collection). The random events are commonplace and hilarious. I could give many many examples but that is pretty much the game in a nutshell. You can also design clothing, customize a town tune, garden, make your town and house exactly the way you want them, come up with sayings for neighbors to say.... the list goes on. The fun is just multiplied as you throw this all online It's cool. Give it a whirl if you get the chance.
Eheheh.... this is where it gets kinda embarrassing for an Animal Crossing fanatic such as I. I have not yet been able to make use of the wifi capabilities. I don't have wifi at my house and can't swing the $40 USB adapter for the DS. I also have not visited the random wifi hotspots Nintendo has conveniently placed at McDonalds. I tried using a friend's wifi connection at their house, but it didn't work and 24 was on, so I had better things to do at that moment
Apparently the way the online set-up works is that you are given a "friend code" and can give the code to other AC players and visit their towns. You can send them mail and items I believe. I know there are many other gamers on this forum who have gone wifi on AC, so they would probably be the ones to ask. I think you can also tear up other people's towns and stuff to, so you have to make sure you let in people you trust I don't know. I don't really like to talk too much about stuff I don't know about, but someone will answer this post in time I'm sure. You should play AC though... it's fun ^_^