The NS, or Name Server records of a domain, reveal which servers deal with the Domain Name System (DNS) records for it. Setting the name servers of a given host company for your domain is the most convenient way to forward it to their system and all its sub-records will be handled on their end. This includes A (the IP address of the server/website), MX (mail server), TXT (free text), SRV (services), CNAME (forwarding), etcetera, so if you want to modify any one of these records, you're going to be able to do it through their system. In other words, the NS records of a domain show the DNS servers which are authoritative for it, so when you try to open a web address, the DNS servers are contacted to get the DNS records of the domain you are attempting to reach. In this way the web site that you're going to see is going to be retrieved from the proper location. The name servers typically have a prefix “ns” or “dns” and each domain address has at least two NS records. There's no sensible difference between the two prefixes, so what kind a hosting provider is going to use depends completely on their preference.