The Name Servers of a domain name show the DNS servers that deal with its DNS records. The IP of the site (A record), the mail server that handles the e-mails 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 forwarded to their hosting platform, it needs to have their name servers, or NS records. If you want 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 name and the request is then pointed to the DNS servers of the webhosting provider where the A record of the web site is retrieved, allowing you to see the content from the right location. Commonly a domain address has a couple of name servers that start with NS or DNS as a prefix and the contrast between the two is just visual.