"The "Z" trigger on the nunchuck will target an enemy. This is a visual target only,a dn is used to help track enemies in the enviroment. You still have to aim the cursor to frag. It is not an aim assist."
The first just locked the camera on to your opponent. If your recticle happened to be on the guy you were shooting, it would stay there. If it wasn't, you'd have to move the recticle to hit your opponent. When you used lock on, you could move the recticle anywhere you wanted.