The Name Servers of a domain name show the DNS servers that handle its DNS records. The IP address of the website (A record), the mail server that manages the emails for a domain (MX records), any text record in free form (TXT record), directing (CNAME record) etc are taken from the DNS servers of the hosting company and for any domain to be using them and to be directed to their hosting platform, it ought to have their name servers, or NS records. If you want to open a site, for instance, and you insert the URL, the browser connects to a DNS server, which keeps the NS records for the domain and the request is then sent to the DNS servers of the webhosting provider where the A record of the site is obtained, allowing you to view the content from the right location. Normally a domain has a couple of name servers that start with NS or DNS as a prefix and the contrast between the two is simply visual.