A Microsoft file hosting and synchronization service.
Hey there, ΛΙΑΠΗΣ ΑΝΑΣΤΑΣΙΟΣ
All that command does is fix any corrupt files in the Windows operating system that Windows uses to run. No data would be removed but if you are worried about your data being removed, please back-up your data onto an external disk before continuing.
Backing up your data is always a good move anyway, especially when trying to troubleshoot the computer and going through recovery options. Another option would be to use the recovery options in Windows to try and resolve this problem. You can reset Windows while keeping your files, but you do have the option to remove everything too. More information about this can be found here: https://support.microsoft.com/en-US/Windows/experience/backup-recovery/reset-your-pc
If you are going down the route of resetting Windows, using the recovery method, please back up your data before continuing.
Hope this helps,
Nathan