What is the use of regedit,

Regedit is a software utility in the Windows operating system used for editing the Windows registry. For more info on the registry and the various versions of the utility, see Wikipedia: Windows Registry.

Editing the registry "for fun" can result in loss of data and result in the computer needing to be profe$$ionally serviced.

Regedit edits your registry.

Fore using reg edit make a backup of your registry file and your data. With everything backed up, even if you mess up badly you can reload.