Answer: Screensavers

If you’re reading this trivia question at a computer, there’s a good chance that two things are true: first, that the operating system on your computer ships with a built-in screensaver system and, two, that you absolutely don’t need it.

In the early days of computing, monitors used the same phosphor-based technology found in old tube televisions, and extended excitement of the same area of the phosphor mesh behind the glass screen would cause burn-in, wherein the phosphors would stay permanently excited and leave a ghost image on the screen.

In order to prevent a monitor left on from having, say, the Windows taskbar burned into it forever, the screensaver would kick on after X number of minutes and move some graphic like pipes, flying toasters, etc. (what it was didn’t matter) around until you returned and, in the process, would prevent any one part of the screen from burning in.

Now, however, the days of widespread CRT and plasma computer monitor use are far behind us and modern flat screen monitors don’t suffer from burn-in as there are no phosphors to overexcite. Today we use screen savers, if we use them at all, for the novelty of it: to display something in the background like slideshows of family photos or exotic locations, and occasionally for security or to display system status information.