What is an icon set you ask? from http://en.wikipedia.org/wiki/Icon_set
A computer icon is a pictogram displayed on a computer screen in order to help user navigate a computer system or mobile device in a similar way traffic signs are used to help a driver navigate traffic; one of the most notable icon designers, Susan Kare was quoted saying "good icons should be more like road signs than illustrations, easily comprehensible, and not cluttered with extraneous detail".[1]Desktop icons for file/data transfer, clock/awaiting, and running a program.
Icons are part of the graphical user interface and belong to the much larger topic of the history of the graphical user interface that has largely supplanted the text-based interface for casual use. The user can activate them using a mouse, pointer, finger, or recently voice commands. Their placement on the screen, also in relation to other icons, may provide further information to the user about their usage.[2] In activating an icon, the user can move directly into and out of the identified function without knowing anything further about the location or requirements of the file or code.