Fences is a program that helps you organize your desktop, and can hide your icons when they're not in use. A "Fence", a term coined by this program, is an icon group on your desktop. Fences is an add-on to your desktop, not a replacement.
Fences allows you to create shaded areas on your desktop that you can place icons in. You can label them however you wish, and move/resize them anywhere on the desktop. Pre-included layouts help speed the process for new users.