For this end of year posting I've taken time-out to explain virtualization in everyday, simple language, using analogies with existing technologies. As always with any attempt to explain things in without getting too technically involved, it's impossible to be exact. More knowledgeable readers will have to forgive me if it seems I cut a few corners.
Chopping-up computers
Virtualization is the practice of running several operating systems at the same time on a single computer.
The multiple operating systems are unaware they're virtual, and are usually unaware of each other. Each believes it's running exclusively on the computer.
Why would anybody want to do this? Do you recall the scene in Fantasia where Mickey Mouse chops the broom in half, only to find it makes more brooms?