The Name Servers of a domain point out the DNS servers that handle its DNS records. The IP of the website (A record), the mail server that deals with the emails 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 hosting provider and for any Internet domain 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 a website, for example, and you enter the URL, the web 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 webhosting provider where the A record of the web site is retrieved, enabling you to see the content from the proper location. Normally a domain name has a couple of name servers that start with NS or DNS as a prefix and the difference between the two is only visual.