This is for hiding a manual from viewers. You will still be able to see the manual from the Admin view.
All content within the manual will be hidden from users while they browse your site, but it will still appear in search results unless you also unpublish the chapters and articles within the manual.
If the manual is already published, then you will have the option to Unpublish it. If the manual is not published, you will have the option to publish it.