Initially, screensavers were developed to prevent phosphor burn-in on CRT monitors, which appeared when computers went idle.
The first screensavers only displayed pictures and animated strings of text. Currently, they include high-quality 3D animations or image slideshows.
Some developers have created screensavers which lock the screen when they are launched and require users to specify the correct password to allow access to the computer desktop.
Screensaver creators provide users with the necessary tools to design professionally-looking screensavers featuring their own pictures, animations or videos.