Adverse Yaw

When an airplane makes turns it needs to change the amount of lift on either wing in order to bank. This is usually done by lowering the aileron on one side and raising the aileron on the other.

The wing with the raised aileron will have less lift than it did before, and the wing with the lowered aileron will have more lift.

The increased lift causes an increase in induced drag which will cause the airplane to yaw towards the wing with more drag.

When a bank is entered the rising wing has more drag so the aircraft will yaw away from the direction of the turn. This is adverse yaw.

Source: FAA Pilot’s Handbook of Aeronautical Knowledge

It can be counteracted easily by using the rudder while banking.

Some planes use spoilers instead of ailerons and they reduce or remove the adverse yaw effect. There is also something called a frise aileron that adds drag to the aileron that is raised to counteract adverse yaw.