The Name Servers of a domain name reveal the DNS servers that deal with its DNS records. The IP 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 taken 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 an Internet site, for example, and you type in the URL, the Internet browser connects to a DNS server, which keeps the NS records for the domain and the request is then pointed to the DNS servers of the webhosting provider where the A record of the website 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 difference between the two is only visual.