The Name Servers of a domain name reveal the DNS servers that manage its DNS records. The IP address of the website (A record), the mail server that manages the e-mails for a domain (MX records), any text record in free form (TXT record), directing (CNAME record) and so forth are obtained from the DNS servers of the website hosting company and for any domain to be using them and to be pointed to their hosting platform, it should have their name servers, or NS records. If you want to open a site, for example, and you insert the URL, the browser connects to a DNS server, which keeps the NS records for the domain address and the request is then forwarded to the DNS servers of the hosting company where the A record of the website is retrieved, so that you can look at the content from the proper location. Commonly a domain address has two name servers that start with NS or DNS as a prefix and the distinction between the two is simply visual.