Wallpaper is the background image on one's "desktop" or "home screen."
Wallpapers vary from system to system both in function and nomenclature. In Mac OS X, the wallpaper is called the "desktop picture." It is a static image or series of images that the operating system cycles through. Its function is purely decorative. In addition to traditional (static) wallpapers, Android (v2.1+) offers "live wallpapers." Live wallpapers are similar to normal applications, though slightly different (they are services rather than activities, so their capabilities are not quite the same). Live wallpapers extend the traditional wallpaper concept by allowing for interactivity, animation, and access to system functions. One of the challenges facing the live wallpaper developer is that the wallpaper is often overlaid with icons, widgets, and the like, beyond the programmer's ability to control or often even to detect.
