Read-only is a file/folder attribute that allows only a specific group of users to modify those files and folders. This feature does not allow others to modify these read-only files/folders without your explicit permission. Depending on your needs, you can leave some files in system mode and others in read-only mode. You can turn this feature on/off at any time.
Unfortunately, several users have reported that their files and folders keep returning to read-only mode after upgrading to Windows 10.