The Name Servers of a domain name reveal the DNS servers that handle its DNS records. The Internet protocol address of the website (A record), the mail server that takes care of the emails for a domain name (MX records), any text record in free form (TXT record), forwarding (CNAME record) and so on are taken from the DNS servers of the website hosting company and for any domain to be using them and to be forwarded to their hosting platform, it should have their name servers, or NS records. If you want to open a website, for example, and you input the URL, the Internet browser connects to a DNS server, which keeps the NS records for the domain name and the request is then sent to the DNS servers of the hosting provider where the A record of the website is retrieved, so that you can view the content from the correct location. Commonly a domain has a couple of name servers that start with NS or DNS as a prefix and the contrast between the two is just visual.