The Name Servers of a domain name point out the DNS servers that deal with its DNS records. The IP address of the website (A record), the mail server that deals with the e-mails for a domain (MX records), any text record in free form (TXT record), directing (CNAME record) and so on are extracted from the DNS servers of the hosting provider and for any domain to be using them and to be forwarded to their hosting platform, it has to have their name servers, or NS records. If you wish to open a site, for instance, and you enter the URL, the browser connects to a DNS server, which keeps the NS records for the domain and the request is then redirected to the DNS servers of the hosting company where the A record of the site is obtained, allowing you to view the content from the correct location. Ordinarily a domain name has 2 name servers that start with NS or DNS as a prefix and the difference between the two is only visual.