Defragment

Defragment - When you constantly add and delete files on your hard drive, they become fragmented.

Think of it like this: You have a library full of collections of books. Each of these collections represents a file on your hard drive. You take one book from the collection and put some sticky notes in the book and make it too big to fit back on the shelf–so you put it on the end. Every now and then you get a new book for a collection; these too need to go on the end of the shelf. You sell a collection and buy a bigger one to replace it. Unfortunately, the whole collection doesn’t fit in the recently made space so you put half in the space and half at the end of the shelf. You do this for years and you have a mess on your hands. Defragmenting “re-orders your book collections” in terms of your data, and makes access to them a lot easier.