The Name Servers of a domain name point out the DNS servers that manage its DNS records. The IP address of the website (A record), the mail server that takes care of the e-mails for a domain (MX records), any text record in free form (TXT record), pointing (CNAME record) etc are extracted from the DNS servers of the hosting provider and for any domain name to be using them and to be pointed to their hosting platform, it should have their name servers, or NS records. If you would like to open a website, for instance, 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 sent to the DNS servers of the hosting company where the A record of the website is retrieved, enabling you to look at the content from the correct location. Ordinarily a domain address has a couple of name servers that start with NS or DNS as a prefix and the distinction between the two is simply visual.