The Name Servers of a domain name point out the DNS servers that are responsible for its DNS records. The IP address of the web site (A record), the mail server that manages the emails for a domain name (MX records), any text record in free form (TXT record), forwarding (CNAME record) etc are extracted 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 ought to have their name servers, or NS records. If you want to open an Internet site, for example, and you input the URL, the web browser connects to a DNS server, which keeps the NS records for the domain and the request is then forwarded to the DNS servers of the hosting provider where the A record of the web site is obtained, enabling you to view the content from the correct location. Usually a domain name has two name servers that start with NS or DNS as a prefix and the contrast between the two is simply visual.