Q: What does it do that the wii remote doesn't? Im confused.
A: Wii Motion Plus is an attachment for the Wiimote that also appears to have a port for plugging a Nunchuk into it. The internals of the Wii Motion Plus is nothing more than another accelerometer, just like the ones in the Wiimote and Nunchuk. By having 2 accelerometers at two different locations in the Wiimote, it will be able to tell the difference between a flick of the wrist and a wide swing of your arm. It will also be much more capable of differentiating between gravity and the centripetal force of a strong swing.