Friend Codes & Etc Questions

Sorry, but I couldn't find much help, and I looked. So...do friend codes come with DS (I hear of them mainly with the Wii), how do you figure what your's is, do you have to have some way to connect to the internet to trade or battle with Wi-Fi, pretty much those basics, really, that I should know and couldn't find answers to. I'd really, really appreciate the help, and thanks.

Once you complete a certain task in the beginning of the game, you will be given a Friend Code Book, on the lower floor of the Pokémon Center.
From that moment you are able to use the WiFi function of the game. When you connect to the WFC, you will get your own Friend Code assigned, which you can view through the Friend Code Book. That is also the place where you can add new friends by their codes.

Your can either battle and trade with your friends directly using the lower floor of the Pokémon Center (or the first floor for Local connecion), or Trade through the Global Trade Station later in the game, as well as battle with other random people in the Battle Tower, which will be accessable near the end.

The direct friend trading/battling can be done in 2 ways:
- WiFi (Internet)
- Local (People that sit near you using the DS' LAN function)

For the first method, you will either need a compatible WLAN router, or a Nintendo WIFi USB Connector.

The second method works with all DS' that are around you.