Ever since the Macintosh was introduced in 1984, icons have been the way we view files on computers. An icon on your computer screen represents an object or a program on your hard drive. For example, the folders you see on your desktop or in open windows are icons. The files that you see in those folders are also icons. The trash can on the Macintosh and the recycle bin on Windows are both icons as well.
Icons are a visual representation of something on your computer. For example, a blue "e" on your screen most likely repersents the Internet Explorer program. An icon that looks like a sheet of paper is probably a text document. By clicking and dragging icons, you can move the actual files they represent to various locations on your computer's hard drive. By double-clicking an application icon, you can open the program. Icons are one of the fundamental features of the graphical user interface (GUI). They make computing much more user-friendly than having to enter text commands to accomplish anything. Some Unix nerds would beg to differ, but I'm talking about normal people here.