The Name Servers of a domain name point out the DNS servers that are responsible for its DNS records. The IP 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), pointing (CNAME record) etc are obtained from the DNS servers of the website hosting provider and for any domain to be using them and to be pointed to their hosting platform, it needs to have their name servers, or NS records. If you want to open a website, for example, and you type in the URL, the web browser connects to a DNS server, which keeps the NS records for the domain and the request is then pointed to the DNS servers of the hosting company where the A record of the website is obtained, enabling you to view 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.