A screensaver is a computer program that activates when a device is idle for a certain period. Originally designed to prevent screen burn-in on older CRT monitors, screensavers now serve various purposes, including providing visual entertainment and displaying information. They can feature animations, images, or even useful data like the time and date. Most modern operating systems, such as Windows and macOS, come with built-in screensavers, and users can often customize them. Screensavers can also be used for security, as they can require a password to exit, helping to protect sensitive information when a user steps away from their device.