The Name Servers of a domain name reveal the DNS servers that are responsible for its DNS records. The IP address of the site (A record), the mail server that handles the e-mails for a domain (MX records), any text record in free form (TXT record), pointing (CNAME record) and so on are obtained from the DNS servers of the web hosting company and for any domain to be using them and to be directed to their hosting platform, it should have their name servers, or NS records. If you wish to open an Internet site, for instance, and you insert the URL, the browser connects to a DNS server, which keeps the NS records for the domain name and the request is then forwarded to the DNS servers of the hosting provider where the A record of the site is obtained, so that you can see the content from the proper location. Usually a domain has a couple of name servers that start with NS or DNS as a prefix and the distinction between the two is simply visual.