A burn-in may refer to any of the following:
1. A burn-in describes turning on and leaving on an electronic device for a predetermined time to prevent any premature failures. Often, a computer or other electronics maker performs a burn-in before shipping a device to help identify and prevent failures.
2. A ghost image or burn-in is an issue that happens when non-moving images or text is displayed on a computer monitor for an extended time. The non-moving object can burn into the monitor's phosphors, remaining faintly visible even when the monitor is off.
This issue occurs mostly with older CGA (color graphics adapter) and EGA (enhanced graphics adapter) CRT (cathode ray tube) monitors, but can still happen with new CRT monitors, although not as common. To help prevent a burn-in, turn the monitor off or use a screen saver when not at the monitor.
If this happens on your monitor, try degaussing the monitor to fix the burn-in. Unfortunately, most burn-ins are permanent and never entirely disappear from the monitor.