Generally speaking, a simple pictorial representation of an object or concept, usually comprising an image that readily conveys what it represents. In Russia, icons are portraits of religious figures, such as Christ, while here in the West in the twentieth-century, icons are used to convey such things as traffic laws (the octagonal shape and red color of a stop sign), conveniences (the symbols found on rest room doors), etc.
In computers, icons are the basic elements that constitute a graphical user interface, which is also sometimes called an iconic interface. Files, programs, utilities, disks, etc., are represented as pictorial symbols—a document looks like a small piece of paper, a directory or sub-directory looks like a manila folder, a disk looks like a disk, a delete function looks like a trash can, etc.—which can be moved about the screen, copied to other media, deleted, or clicked on (using a mouse). Various applications use icons to represent menu items; a symbol of a printer may represent a print function, for example.
The goal of a good icon is to convey what it means directly and simply. As we know from experience, however, this isn't always the case.