The Name Servers of a domain name point out the DNS servers that are responsible for its DNS records. The IP address of the site (A record), the mail server that handles the emails for a domain name (MX records), any text record in free form (TXT record), pointing (CNAME record) and so on are obtained from the DNS servers of the hosting provider and for any domain address to be using them and to be directed to their hosting platform, it ought to have their name servers, or NS records. If you wish to open a site, for instance, and you type the URL, the browser connects to a DNS server, which keeps the NS records for the domain name and the request is then sent to the DNS servers of the webhosting provider where the A record of the site is obtained, enabling you to look at the content from the proper location. Commonly a domain name has two name servers that start with NS or DNS as a prefix and the difference between the two is just visual.