The Name Servers of a domain name point out the DNS servers that deal with its DNS records. The IP address of the website (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 forth are taken from the DNS servers of the website hosting company and for any domain address to be using them and to be pointed to their hosting platform, it has to have their name servers, or NS records. If you want to open a website, for instance, and you insert the URL, the web browser connects to a DNS server, which keeps the NS records for the domain 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 view the content from the correct location. Normally a domain has a couple of name servers that start with NS or DNS as a prefix and the difference between the two is just visual.