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 e-mails for a domain name (MX records), any text record in free form (TXT record), directing (CNAME record) etc are extracted from the DNS servers of the web hosting company and for any domain name to be using them and to be forwarded to their hosting platform, it should have their name servers, or NS records. If you would like to open a website, for instance, 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 webhosting provider where the A record of the web site is obtained, allowing you to see the content from the right location. Normally a domain has 2 name servers that start with NS or DNS as a prefix and the difference between the two is only visual.