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The display resolution of a digital television or computer display typically refers to the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by all different factors in cathode ray tube (CRT) and flat panel or projection displays using fixed picture-element (pixel) arrays.

The terms wallpaper and desktop picture refer to an image used as a background on a computer screen, usually for the desktop of a graphical user interface. 'Wallpaper' is the term used in Microsoft Windows, while the Mac OS calls it a 'desktop background' (prior to Mac OS X, the term desktop pattern was used to refer to a small pattern that was repeated to fill the screen).

A screensaver is a type of computer program initially designed to prevent "Phosphor burn-in" on CRT and plasma computer monitors by blanking the screen or filling it with moving images or patterns when the computer is not in use. Today, screensavers are also used for entertainment or security.
Before the advent of LCD screens, most computer screens depended on cathode ray tubes (CRTs). When the same image is displayed on a CRT screen for long periods of time, the properties of the exposed areas of phosphor coating on the inside of the screen gradually and permanently change, eventually leading to a darkened shadow or "ghost" image on the screen. Televisions, oscilloscopes and other devices that use CRTs are all susceptible to phosphor burn-in, as are plasma displays to some extent.

Screensaver programs were designed to help avoid these effects by automatically changing the images on the screen during periods of user inactivity.

For CRTs used in public, such as ATMs and railway ticketing machines, the risk of burn-in is especially high because a stand-by display is shown whenever the machine is not in use. Older machines designed without burn-in problems taken into consideration often display evidence of screen damage, with images or text such as "Please insert your card" (in the case of ATMs) visible even when the display changes while the machine is in use. Blanking the screen is out of the question as the machine would appear to be out of service. In these applications, burn-in is prevented by shifting the position of the display contents every few seconds, or by having a number of different images that are changed regularly.

Modern CRTs are much less susceptible to burn-in than older models due to improvements in phosphor coatings, and because modern computer images are generally lower contrast than the stark green- or white-on-black text and graphics of earlier machines. LCD computer monitors, including the display panels used in laptop computers, are not susceptible to burn-in because the image is not directly produced by phosphors (although they can suffer from a less extreme and usually non-permanent form of image persistence). For these reasons, screensavers today are primarily decorative or for entertainment, and usually feature moving images or patterns and sometimes sound effects.

One increasingly popular application is for screensavers to activate a useful background task, such as a virus scan or a distributed computing application (such as the SETI@home project). This is convenient because these applications only use resources when the computer would be otherwise idle.