A LiveCD can be put into the computer, and then the linux operating system that is on the CD will run on your computer from this CD without changing your computer in any way - neither the configuration of it, or the data you have lying on it. This makes it possible to test the new operating system without "touching" your computer.


Some Linux versions offer a decidedly LiveCD, while others allow you to try the operating system from the installation CD before any installation. 

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