The Name Servers of a domain reveal the DNS servers that deal with its DNS records. The IP 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), pointing (CNAME record) etc are taken from the DNS servers of the web hosting provider and for any Internet 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 input the URL, the Internet browser connects to a DNS server, which keeps the NS records for the domain and the request is then redirected to the DNS servers of the webhosting provider where the A record of the site is obtained, so that you can look at the content from the right location. Normally a domain has a couple of name servers that start with NS or DNS as a prefix and the distinction between the two is just visual.