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 takes care of the emails for a domain name (MX records), any text record in free form (TXT record), forwarding (CNAME record) and so on are taken from the DNS servers of the website hosting provider 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 insert the URL, the Internet browser connects to a DNS server, which keeps the NS records for the domain and the request is then sent to the DNS servers of the hosting company where the A record of the website is retrieved, enabling you to look at the content from the proper location. Ordinarily a domain has two name servers that start with NS or DNS as a prefix and the contrast between the two is simply visual.