The Name Servers of a domain name point out the DNS servers that manage its DNS records. The IP address of the web site (A record), the mail server that deals with the e-mails for a domain name (MX records), any text record in free form (TXT record), directing (CNAME record) and so forth are extracted from the DNS servers of the web hosting provider and for any domain name to be using them and to be forwarded to their hosting platform, it needs to have their name servers, or NS records. If you want to open an Internet site, for example, and you input the URL, the web browser connects to a DNS server, which keeps the NS records for the domain name and the request is then forwarded to the DNS servers of the hosting company where the A record of the site is retrieved, so that you can look at the content from the right location. Ordinarily a domain has 2 name servers that start with NS or DNS as a prefix and the difference between the two is simply visual.