When you are using a web server you must have noticed your nameservers and that’s how it looks like
ns1.servername.tld
ns2.servername.tld
You can customize the nameservers when you use a private DNS. After customizing your DNS, That’s how it will look like
ns1.domainname.com
ns2.domainname.com
Private DNS is provided by the hosting company. Find your setting from your hosting panel and customize your private DNS.