ICON
A sign is an icon if it looks like some object that the reader remembers
having encountered in the past. For example, the image on this page is
definitely not alive. But because it resembles a living animal, the reader is
reminded of an actual frog.
The sign that you see on the screen is produced by a collection of pixels,
some of which project green light, some of which project blue light, and so
on. When you perceive the pattern of light, it reminds you of a frog. This is
how iconic signs work.