The Name Servers of a domain reveal the DNS servers that deal with its DNS records. The Internet protocol address of the web site (A record), the mail server that takes care of the emails for a domain name (MX records), any text record in free form (TXT record), pointing (CNAME record) and so on are extracted from the DNS servers of the web hosting provider and for any domain name to be using them and to be forwarded to their hosting platform, it ought to have their name servers, or NS records. If you want to open an Internet site, for instance, and you insert the URL, the web browser connects to a DNS server, which keeps the NS records for the domain address and the request is then sent to the DNS servers of the hosting provider where the A record of the web site is retrieved, allowing you to view the content from the right location. Commonly a domain address has two name servers that start with NS or DNS as a prefix and the distinction between the two is just visual.