Overlay

Overlay refers to the placement of one visual element on top of another, such that both may be seen. In technology and media, an overlay describes a layer that sits above base content and can be added, modified, or removed without altering the underlying material.

In digital graphics and video, overlays are graphics, text, or symbols composited on a base image or frame. They use transparency or alpha channels to blend with the background. Common uses include captions, logos, weather icons, and UI hints.

In user interfaces, overlays are UI layers that appear over the main content, such as modal dialogs, tooltips, and floating panels. In augmented reality and mapping applications, overlays display information on top of a live view or map, enabling context without navigating away.

In geographic information systems, overlay analysis combines multiple spatial datasets to produce a new layer or result, using operations like intersection, union, difference, and attribute joins.

In networking and systems, overlay networks create virtual topologies on an existing physical network, enabling flexible routing and services. Examples include virtual private networks and peer-to-peer networks. In file systems, overlay filesystems layer directories to present a single view.

In broadcasting and media production, overlays include on-screen graphics such as captions or lower thirds. They are designed to be informative without obscuring core content.