Here's the "online" thing.
Nintendo thinks that videogames are doomed. Not right away, but "soon". So do a lot of other companies, but Nintendo has been saying it the longest and the clearest. "Standout graphics" are getting harder and harder to produce, and they're having less and less of an effect in getting people to buy games.
Nintendo thinks that the way to head this off is to make gaming "simple" so that anyone can pick something up and play it, and at the same time they think that developers need to put out constant creativity and innovation.
Many companies like Square think that the future of videogames lies in making an online game, and charging people to play the game.
Nintendo isn't opposed to online, but they think that it only comes in two flavors right now: "complicated" and/or "expensive". Both of which drive people away. Some companies like Microsoft are offering the "expensive" version at a loss, in an attempt to buy popularity, but there's no real future in that.
Nintendo made a broadband adapter for the GameCube, but since Nintendo never made any online games on the GameCube, pretty much nobody else did either.
A group of Nintendo fans calling themselves "Warp Pipe" set up a system where you could hook up your Cube to your computer and use it as a "bridge" over the internet to hook up to other Cubes, and play LAN-enabled games over the internet. It wasn't extremely popular, even though it's free, probably because Warp Pipe was just a small fan-group, and possibly because most people thought it must be complicated. But Nintendo was apparently impressed with them, because a while later WP's president said at E3 that he had met with Nintendo, and that Warp Pipe software would be coming built-in with all future LAN-enabled GameCube games, giving them free-and-simple online. But then Warp Pipe clammed up. None of these games appeared.
With the DS, Nintendo included a Wi-Fi connection. That's wireless broadband, built-in. If you have a wireless hub, your DS can connect to your computer, and your interent connection, effortlessly. But we can't say exactly how this works, because no games have used the Wi-Fi yet. Even though some developers have said it's a piece of cake. Nintendo would not have wasted money to put the Wi-Fi there for no reason.
With the DS, Warp Pipe has re-emerged. They're apparently working on something super-top-secret called DemaSked. They won't say what it is, because they have really tight legal contracts saying that they can't. We can assume it's at least for the DS, because of the way they highlight those letters. They drop a lot of cryptic clues about it though. Some seem to say that it's some sort of "online" something-or-the-other for the DS. While (AFAIK) Warp Pipe themselves have said that it's not "Warp Pipe for the DS". Supposedly Warp Pipe's getting money from somewhere, presumably Nintendo. All we really know about Demasked is that it's supposed to be super-fantastic, and that we'll know more soon. It's supposed to get unveiled around the time when the PSP launches in America (which could mean that it's also being made for the PSP, or that Warp Pipe is making sure that it's too late for Sony to change course), or perhaps around the time that the Revolution gets unveiled at E3 (which might mean that it's also for the Revolution somehow).
Perhaps independant from whatever Warp Pipe is working on, Shigeru Miyamoto supposedly mentioned in Japan recently that he was working with Square to set up an online system for the DS.
There. I think you're up to date now (assuming you read all of that).