Adverse Yaw
Adverse yaw is the tendency for an airplane to yaw in the opposite direction of a bank. For example, if you roll to the right, you'll experience an adverse yawing moment to the left.
This is because the lower wing (the inside wing) momentarily producing less lift than it was previously. This decrease in lift also comes with a decrease in induced drag, and the wing has a tendency to move forward.
Likewise the outside wing is momentarily producing more lift, which causes an increase in induced drag and "pulls" the wing backward.
Counteracting Adverse Yaw
Most light airplanes are fitted with differential ailerons to counteract the effects of adverse yaw. With these, the upward alerion travels further upward than the downward aileron travels downward. This deceases the amount of drag produced by the upward moving wing.
As always though, rudder input will still be required to coordinate the turn.