What is wii fii??

Do you mean Wii Fit?
Wii fit a an accessory of Wii (video game machine develop by Nintendo). Actually, Wii fit is a balance board and you can play various mini games by standing on the board and shift your balance point (as a control device by minor body movements).
You can follow the program / game disc instructions (show on TV) to do balance exercises and yoga! It's quite an interesting and innovative gaming experience!

wii Fit 係任天堂就wii出既新遊戲套裝, 呢個新遊戲係要用一個平衡板來配合, 套裝內包括一些小遊戲及一些yoga動作, 玩家要跟據唔同遊戲/yoga 的要求做出一些動作, 例如,滑雪,行鋼線及sit up 等等.

所以要玩wii Fit, 一定要買咗wii先