The Name Servers of a domain reveal the DNS servers that handle its DNS records. The Internet protocol address of the website (A record), the mail server that manages the e-mails for a domain address (MX records), any text record in free form (TXT record), forwarding (CNAME record) etc are obtained from the DNS servers of the web hosting provider and for any domain to be using them and to be directed to their hosting platform, it should have their name servers, or NS records. If you want to open an Internet site, for instance, 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 sent to the DNS servers of the hosting provider where the A record of the web site is obtained, so that you can view the content from the correct location. Commonly a domain name has 2 name servers that start with NS or DNS as a prefix and the contrast between the two is just visual.