Backspin is a technique used in sports like tennis and golf to create a rotational force on the ball. When a player strikes the ball with a specific angle and speed, it causes the ball to spin backward as it travels through the air. This spin can affect the ball's trajectory and bounce, making it more challenging for opponents to return. In tennis, backspin can help keep the ball low and slow, allowing for better control during rallies. In golf, backspin can help the ball stop quickly on the green, giving players more precision with their shots.