A screen saver is a computer program that displays a series of images or animations on a computer or mobile device screen when it is idle for a certain period of time. Screen savers were originally designed to prevent burn-in on CRT monitors by constantly changing the image on the screen. Today, they are used primarily for entertainment or to provide information or advertising. Screen savers can display a variety of content, such as photos, graphics, animations, or text, and can be customized to suit individual preferences. They can be activated manually or set to automatically activate after a specified period of inactivity.