This image shows a top-side view of a ball spinning in motion. The axis is perpindicular to the flow of air across it. According to Bernoulli's principle the pressure is reduced because "The air travels faster relative to the center of the ball where the periphery of the ball is moving in the same direction as the airflow (left)." Also, The pressure increases on the other side of the ball, where the air travels slower relative to the center of the ball (right)." This creats an imbalance on the forces, deflecting the ball in the sam sense of spin, from bottom right to top left, creating the "Magnus Effect".