What is ghosting in computers?

Many kinds of ghosting

From http://en.wikipedia.org/wiki/Ghosting:
Ghosting can have different meanings:
(among them:)

• The act of creating a completely identical copy, or a ghost image, of a hard diskbackup software such as Ghost, on to removable media or a network drive to be used as a backup copy of a PC in case a restore of that PC is required.
• A problem in LCD screens when tiny pixels creating the image take time to switch on and off and can't do it fast enough. The problem, widely recognized as the main drawback of LCD screens, is apparent in fast moving objects such as tennis balls, but even slower moving images get fuzzy. This can happen especially when the device is exposed to cold for long periods of time. Most modern LCD screens no longer have this problem.

• A technique used in online games, usually team-based 'last man standing' first-person shooters, where dead players inform their team mates who are still alive of the whereabouts of the enemy: this is generally considered cheating.

• When a person (on AOL) seems as though they signed off, but in fact they are online. All they have done is change their settings to block all users from seeing them. Ghosting can also be done under Windows Live Messenger, Yahoo Instant Messenger, etc, when a user has their status set as 'Appear offline'. This still allows the user to send messages to other users, to whom the user appears offline.

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