JPerrone, to answer your question 'what is adverse yaw' :
(this example is specific to using ailerons to bank the airplane)
when a wing creates lift, (by moving through a relatively stationary air mass) that wing also creates drag,
but it does so at a different rate. in other words, if you double the amount of lift a wing is making, you increase the drag it's making by 4.
in the case of an airplane using it's ailerons to bank, (lets say to the left) the left aileron goes up, the right aileron goes down.
the right wing begins to make more lift that the left wing, therefore the right wing begins to make significantly more drag, while at the same time the left wing makes significantly LESS drag.
think about it: we're banking the airplane to the left, during a left turn, the left wing has a SHORTER distance to travel, yet the right wing is making much more drag than the left wing is.
and that at the end of the day is the 25 cent version of why rudder is (usually) needed during a banked turn in the first place.
the more adverse yaw created, the more rudder is needed.

by using differential aileron control, we make the ailerons move UP more than they do down.
the goal is to make it so the difference in the amount of drag each wing panel makes is not as drastic.