An overlay, or layer, is a graphical element that is placed on top of another image or background in digital design. It can be used to enhance visuals by adding effects, text, or additional images without altering the original content. Overlays are commonly used in applications like Adobe Photoshop and Canva to create visually appealing designs. In web design, overlays can also refer to elements that appear over a webpage, such as pop-up menus or modal windows. These overlays help to focus user attention on specific content or actions, improving the overall user experience while maintaining the underlying page's structure.