What is disk formatting? What does it actually do?
And another here:
There's an excellent article on the subject in Wikipedia (http://en.wikipedia.org/wiki/Disk_formatting). In summary, it's the process of preparing a drive (or more acurately, a volume) for initial use. The details vary significantly between operating systems and devices, and there are also different "levels" of formatting (low-level, high-level and "quick") and they work differently, but the aim of all of them is to end up with a disc which is ready for use.