The Name Servers of a domain name show the DNS servers that manage its DNS records. The IP of the website (A record), the mail server that takes care of the e-mails for a domain address (MX records), any text record in free form (TXT record), forwarding (CNAME record) etc are obtained from the DNS servers of the web hosting company and for any domain to be using them and to be pointed to their hosting platform, it should have their name servers, or NS records. If you wish to open a site, for example, 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 forwarded to the DNS servers of the hosting company where the A record of the site is retrieved, enabling you to look at the content from the correct location. Normally a domain name has 2 name servers that start with NS or DNS as a prefix and the contrast between the two is simply visual.