When you register domain it is required by protocol to specify at least 2 name servers, but sometimes it is necessary to own domain for resale and you cannot show it for public because it can violate some trademark and you may receive abuse report frequently.
In this case you can use our Black Hole NS. What does it mean? These name servers do not return any DNS record, but you can register and own domain with them.
Black Hole NS Advantages:
Domain will not be visible in browser (will not work)
Domain can be registered
Domain does not violate any trademark (it does not work at all)
Useful for domainers who sell domains
Domain does not show website or any page even parking page.
Black Hole NS Drawbacks:
Domain does not work in browser (use Regery NS instead)
So, if you want to hide domain worldwide use Black Hole NS.