what is a screensaver

A screensaver is a computer program that blanks the display screen or fills it with moving images or patterns when the computer has been idle for a specified period of time. Its original purpose was to prevent phosphor burn-in on CRT or plasma computer monitors, though most modern monitors are not susceptible to this issue. Screensavers are also used to provide a basic layer of security by requiring a password to resume the computer, and some can activate useful background tasks, such as virus scans or volunteer computing applications. Additionally, they can be set to offer entertainment and protection by displaying moving images, cartoons, or other visuals when the computer is idle