The Name Servers of a domain reveal the DNS servers that are responsible for its DNS records. The IP address of the web site (A record), the mail server that takes care of the e-mails for a domain name (MX records), any text record in free form (TXT record), forwarding (CNAME record) and so forth are obtained from the DNS servers of the web hosting company and for any domain to be using them and to be forwarded to their hosting platform, it needs to have their name servers, or NS records. If you wish to open a website, for instance, and you type in the URL, the web browser connects to a DNS server, which keeps the NS records for the domain name and the request is then redirected to the DNS servers of the hosting provider where the A record of the web site is obtained, so you can view the content from the correct location. Ordinarily a domain name has two name servers that start with NS or DNS as a prefix and the difference between the two is simply visual.