The Name Servers of a domain show the DNS servers that handle its DNS records. The IP of the web site (A record), the mail server that handles 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 provider and for any domain name to be using them and to be pointed to their hosting platform, it needs to have their name servers, or NS records. If you would like to open a website, for example, and you enter the URL, the Internet browser connects to a DNS server, which keeps the NS records for the domain name and the request is then redirected to the DNS servers of the hosting provider where the A record of the web site is retrieved, so you can view the content from the correct 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 simply visual.