What is a file defrag?
As you use your computer files are created - sometimes by your own intention, and some in the background by applications you’ve installed or downloaded. These files, once they’re on your disk (hard drive) become fragmented (visit ask-leo.com for a deeper explanation).
Fragmented files are slower to access because your computer has [...]

Since computers store information in various places on your computer (called fragmentation) it becomes difficult for the computer to perform quickly when this information is stored throughout the hard drive. For this reason, there are defragmentation tools that take the informational pieces from opposite ends of the computer and put them in more accessible [...]

On your computer there are built in files.  Whenever you use the computer, there is information that can be thought of as papers that are filed into the appropriate files on your computer.  All of this is done automatically, not including the files you create for your information.  While you are using your computer the [...]