Icons (as per Wikipedia) in the field of computing are small pictograms used to supplement the normal alphanumeric of computers, used to aid the user recognize computer interfaces . They are usually 16×16 pixels , upto 128 x 128 pixels in dimension. Answers defines icons as image or representation. Icons are regularly used in computer desktops to denote or identify clickable programs or files and folders  inside your  computer .

Icons also widely used in the field of web design , sometimes to enhance the visual display of the layout and sometimes also for better usability.

How does icons induce better usability ? : Usability guru Jacob Nelsen refers 5 quality components of usability as ” Learnability , Efficiency , Memorability , Errors and Satisfaction ( read more ). Icons easily identifies key areas in a layout  by the graphical element , like  helps a layman to understand he can run a print command / take a print out , or view the printer friendly version of the page by clicking that . Or maybe , this helps them to understand the skype id of the site owner is available or by clicking it , the visitor can skype him. Same way , icons also provides memorability , like for example a Search Icon in a layout wherever it maybe or a RSS / feed icon   on a blog etches a mark in their memory that they can always subscribe to its content from offsite .