The definition of an icon is a graphic representation of something, a person or thing that is symbolic or is a noted figure.

On a Web page, an icon is often a graphical image that represents the topic or information category of another Web page. Frequently, the icon is a hypertext link to that page. Typically, icons are gathered in one or two places on a page, either as separate graphic files or as a single image map.

In computing, an icon is a pictogram displayed on a computer screen in order to help the user navigate a computer system or mobile device. The icon itself is a quickly comprehensible symbol of a software tool, function, or a data file, accessible on the system and is more like a traffic sign than a detailed illustration of the actual entity it represents.

Icons are very useful in applications that use windows, because with the click of a mouse button you can shrink an entire window into a small icon.