The Name Servers of a domain name reveal the DNS servers that handle its DNS records. The IP of the website (A record), the mail server that takes care of the e-mails for a domain (MX records), any text record in free form (TXT record), pointing (CNAME record) and so forth are obtained from the DNS servers of the website hosting company and for any domain address to be using them and to be pointed to their hosting platform, it should have their name servers, or NS records. If you would like to open an Internet site, for instance, and you input the URL, the browser connects to a DNS server, which keeps the NS records for the domain address and the request is then forwarded to the DNS servers of the hosting company where the A record of the web site is retrieved, allowing you to view the content from the right location. Normally a domain has 2 name servers that start with NS or DNS as a prefix and the contrast between the two is just visual.