The Name Servers of a domain name reveal the DNS servers that deal with its DNS records. The IP of the web site (A record), the mail server that takes care of the e-mails for a domain name (MX records), any text record in free form (TXT record), pointing (CNAME record) and so on are obtained from the DNS servers of the web hosting company and for any domain to be using them and to be pointed to their hosting platform, it should have their name servers, or NS records. If you would like to open an Internet site, for instance, and you input the URL, the web browser connects to a DNS server, which keeps the NS records for the domain and the request is then redirected to the DNS servers of the hosting provider where the A record of the website is obtained, allowing you to look at the content from the right location. Ordinarily 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.