The Name Servers of a domain reveal the DNS servers that handle its DNS records. The Internet protocol address of the web site (A record), the mail server that manages the e-mails for a domain name (MX records), any text record in free form (TXT record), forwarding (CNAME record) etc are extracted from the DNS servers of the website hosting company and for any domain to be using them and to be directed to their hosting platform, it has to have their name servers, or NS records. If you would like to open a site, for instance, and you input the URL, the web browser connects to a DNS server, which keeps the NS records for the domain address and the request is then pointed to the DNS servers of the hosting provider where the A record of the site is retrieved, allowing you to view the content from the proper location. Commonly a domain has two name servers that start with NS or DNS as a prefix and the contrast between the two is only visual.