The Wii is Nintendos Next Gen console. Orginally named The Revolution, they renamed it for potty joke purposes, and just standing out. You think, "Why Wii of all names?"
Because of it's playstyle. Once you get a hold of it, you'll literally be saying "wheeeeeeeeee!" It features a DVD style remote that interacts with the screen, ala Onimusha 3 sword on Onimusha 3, where you slash and it copies your movements on the screen(Only with GREAT detection)
Imagine running and shooting with Samus Aran, while doing it in your own home. Imagine flying, jumping, and jumping on Goombas in Mario Galaxy. In your own home. Imagine Fire Emblem! It's also been stated The Legend of Zelda:Twilight Princess was delayed so it'll be compatible for the Wii.
Besides it's awesome interaction, you can DOWNLOAD free Nintendo games for the Wii. Yes, it's been stated that so far, for any Nintendo system, some select games are downloadable. Reliving the old with the new, the Wii has certainly amazed me. It's my "first to buy" when it hits the stores. Rumored in November.
Like mah little summary? =P
Edit:Oh, and it's also been said it's going to be the cheapest of the three (PS3, X-box 360, and Wii).
So, go out and buy one when it comes out. Or preorder it. As fast as you can.