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.
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.
