Parallax scrolling is a web design technique that creates an illusion of depth by moving background images at a different speed than foreground content. This effect enhances the visual experience, making websites more engaging and dynamic. As users scroll down a page, they perceive layers of content that appear to move independently, creating a sense of immersion. This technique is commonly used in video games and mobile applications to add a three-dimensional feel to the user interface. By manipulating the speed of various elements, designers can guide users' attention and improve storytelling through visual cues, making the overall experience more interactive.