The Name Servers of a domain reveal the DNS servers that deal with its DNS records. The Internet protocol address of the site (A record), the mail server that manages the emails for a domain name (MX records), any text record in free form (TXT record), pointing (CNAME record) and so forth are extracted from the DNS servers of the website hosting provider and for any Internet domain to be using them and to be directed to their hosting platform, it has to have their name servers, or NS records. If you want to open a site, for example, and you type the URL, the Internet browser connects to a DNS server, which keeps the NS records for the domain address and the request is then sent to the DNS servers of the webhosting provider where the A record of the website is obtained, enabling you to see the content from the right location. Commonly a domain name has 2 name servers that start with NS or DNS as a prefix and the contrast between the two is just visual.