Wii:  Wii is a console by Nintendo that uses wireless controllers and can sense motion of those controllers in 3D space.

Mii:  A Mii is a Wii avatar.

PS2/3 etc.:  PS2/3 are consoles by Play Station.

XBox/360:  XBox/360 are consoles by Microsoft.

controllers:  Controllers are the method of interacting with the game consoles and controlling your character and game play.

If we list specific games, should mention Wii Fit.