An overlay is a layer or covering that is placed on top of something else, often to enhance or modify its appearance or function. It can refer to physical materials, such as a transparent sheet placed over a map to show additional information, or to digital elements, such as text or images added on top of a video or image. In a broader sense, an overlay can also describe the act of adding or superimposing something onto an existing structure or system. This term is commonly used in design, technology, and gaming, where overlays are used to provide additional information, create visual effects, or improve user experience. In essence, an overlay is a versatile tool that allows for creative and practical enhancements to be made, without altering the underlying foundation.