The Hard Disk
Everything About It
What is it?
How a Hard Drive works
A hard drive stores all the information ever recorded; even if your computer is off. If you try and delete something, it wont actually be deleted. It will still be on the hard drive. So the only way to really delete something is to destroy the hard disk.
Also the hard disks in a desktop and a laptop are a little bit different.
Everything that is saved onto a hard disk is measured in size: Text is very small; pictures are larger; music is bigger and videos are the biggest.
Here is a video of how it works and to make it easier to see, its been slowed down: