The Name Servers of a domain reveal the DNS servers that deal with its DNS records. The IP 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), forwarding (CNAME record) and so forth are taken from the DNS servers of the web hosting company and for any domain address to be using them and to be forwarded to their hosting platform, it has to have their name servers, or NS records. If you wish to open a website, for example, and you enter the URL, the Internet browser connects to a DNS server, which keeps the NS records for the domain address and the request is then redirected to the DNS servers of the hosting company where the A record of the website is retrieved, so you can view the content from the correct location. Normally a domain address has two name servers that start with NS or DNS as a prefix and the contrast between the two is just visual.