No games use wi-fi yet. They all use the proprietary wireless format the DS uses for local network games. Wi-Fi is 802.11, aka online play. The DS supports this format too. All you need is a wireless router (hooked up to cable or DSL), a DS, and a game that supports Wi-Fi. The first games to support Wi-Fi are likely to be Mario Kart and Metroid Hunters around May/June. Various reputable sources close to Nintendo have reported that both Nintendo and Square are setting up servers for online play. It is not sure if each company will have to have it's own servers for their online games and their own online interface, like the PS2 and PC, or if Nintendo is partnering with a third party (Square or Demasked being the only possible partners at this point) and setting up a centralized interface, like Xbox Live. And that's just the official stuff. You can also play non Wi-Fi games (the ones that only support the proprietary WLAN format like First Hunt and Madden) online using tunneling software and a PC. TeamXlink is already progressing in this regard although I have not checked with them for a while and don't know the current status.