The Name Servers of a domain point out the DNS servers that deal with its DNS records. The IP of the web site (A record), the mail server that handles the e-mails for a domain (MX records), any text record in free form (TXT record), directing (CNAME record) and so on are taken from the DNS servers of the website hosting provider and for any domain address to be using them and to be pointed to their hosting platform, it needs to have their name servers, or NS records. If you would like to open an Internet site, for example, 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 redirected to the DNS servers of the hosting provider where the A record of the web site is retrieved, so that you can look at the content from the correct location. Usually a domain address has two name servers that start with NS or DNS as a prefix and the difference between the two is only visual.