The Name Servers of a domain name reveal the DNS servers that are responsible for its DNS records. The IP of the site (A record), the mail server that deals with the emails for a domain address (MX records), any text record in free form (TXT record), forwarding (CNAME record) and so forth 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 has to have their name servers, or NS records. If you want to open a website, for instance, and you type in the URL, the Internet browser connects to a DNS server, which keeps the NS records for the domain name and the request is then redirected to the DNS servers of the hosting provider where the A record of the site is retrieved, so you can look at the content from the correct location. Ordinarily a domain name has two name servers that start with NS or DNS as a prefix and the distinction between the two is just visual.