The Name Servers of a domain reveal the DNS servers that are responsible for its DNS records. The IP of the web site (A record), the mail server that manages the emails for a domain address (MX records), any text record in free form (TXT record), forwarding (CNAME record) and so on are obtained from the DNS servers of the web hosting company and for any domain address to be using them and to be directed to their hosting platform, it needs to have their name servers, or NS records. If you would like to open an Internet site, for example, and you type the URL, the web browser connects to a DNS server, which keeps the NS records for the domain and the request is then sent to the DNS servers of the hosting company where the A record of the site is obtained, allowing you to see the content from the right 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.