What exactly is WI-FI is it like a cord you plug into your ds or something?
Nope it's the built in feature that lets you connect to another DS wirelessly.
Yes, wi-fi is basically one way of saying wireless. The Nintendo DS has it built in so one DS can connect to another wirelessly, and will use its wireless signals to connect to PC's/Broadband Modems to play online later in the year!
So to go online, the DS's Wi-Fi basically connects to that of a wireless router?
If you have a wireless router, it will connect directly to that (When Nintendo tell you how!

), otherwise you'll have to buy a USB/etc. adapter for your PC/Modem which Nintendo are also making - Because not everyone has a wireless router!

Cool, I get it now. It's cool because I don't have a wireless router.

Niether do i, lol
Theres an adapter that was found circling the net at the beginning of the year, no idea if thats the real thing or not though - Gives you a rough idea of how it might work mind.
I don't think that it actually be it, because it looks suspicuously like someone has just taken a photo of the top of a DS and photoshopped a USB onto it.
It's cool they are going to release a USB adapter like that though, I don't have a wireless router!
Lol, oh yea, so it does, although maybe thats the point!

What you mean they disguised the fact that they were giving out information early by making it look suspisious?
