A wallpaper or background (also known as a desktop wallpaper, desktop background, desktop picture or desktop image on computers) is a digital image (photo, drawing etc.) used as a decorative background of a graphical user interface on the screen of a computer, mobile communications device or other electronic device. On a computer it is usually for the desktop, while on a mobile phone it is usually the background for the 'home' or 'idle' screen. Though most devices come with a default picture, users can usually change it to custom files of their choosing.
"Wallpaper" was the term used in Microsoft Windows before Windows Vista (where it is called the "desktop background"), while Mac OS X calls it "desktop picture". (Previously, the term desktop pattern was used to refer to a small pattern that was repeated to fill the screen.)
Wallpaper images are usually copyrighted as many other digital images found on the Internet, and as such, most websites collecting and sharing wallpapers, as well as the users downloading from them are an example of mass copyright infringement, a phenomenon which challenges the meaning and illegality of digital piracy and the validity of current copyright legislation around the world.