The Name Servers of a domain point out the DNS servers that handle its DNS records. The Internet protocol address of the website (A record), the mail server that takes care of the emails for a domain address (MX records), any text record in free form (TXT record), pointing (CNAME record) etc are taken from the DNS servers of the hosting company and for any domain name to be using them and to be forwarded to their hosting platform, it should have their name servers, or NS records. If you would like to open a site, for example, and you type in the URL, the Internet browser connects to a DNS server, which keeps the NS records for the domain and the request is then pointed to the DNS servers of the webhosting provider where the A record of the web site is retrieved, allowing you to view the content from the proper location. Commonly a domain has two name servers that start with NS or DNS as a prefix and the contrast between the two is just visual.