Yaw is rotation about the vertical axis. For this example, push the left rudder pedal.
As the airplane yaws to the left, the right wing is temporarily pushed forward, and the left wing is temporarily pushed aft, relative to the yaw axis. The temporary increase in speed of the right wing causes increased lift, while the temporary decrease in speed of the left wing causes decreased lift. Therefore the right wing rises, the left wing drops, and the airplane rolls. When the rudder is released, the opposite happens, and the airplane rolls upright again.