An icon is a picture or symbol on a graphical user interface (GUI) that depicts a program or command. The term comes from the Greek word eikon, which means likeness, image or portrait.
The mouse interacts with an icon in several ways. This usually initiates some action, such as causing a program to run, a file to be displayed or to open.
Among the trends with regard to icons in recent years have been higher resolution, image like realism and glossy effect. Sizes range from as little as 16 by 16 pixels to as maximum as 128 by 128 pixels, according to the operating system and display settings.
The creation of good icons is a highly specialized skill that requires both artistic talent and an understanding of usability concepts and different perspective view as well as user friendly.
The well rendered icons may not loose clarity when it is down scaled, it should adopt wide variety of display monitors set at various resolutions.