You really need to be more familiar with a computers operating system than to be messing with it. I say that because you ask what is it and how to use it. It is a basic feature of Windows operating system and was used with DOS. You need to be sure and safe guard and data you want to keep befor running it. Just incase you loose all your data. I have seen it done many times and folks come to me asking for a hard disk recovery. Do you have a friend that could come by and help? Where are you located at?