The NS, or Name Server records of a domain, reveal which servers handle the Domain Name System (DNS) records for it. Setting the name servers of a specific host company for your domain address is the most effective way to forward it to their system and all its sub-records will be taken care of 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, in case you want to modify any one of these records, you will be able to do it through their system. Put simply, the NS records of a domain address reveal the DNS servers which are authoritative for it, so when you try to open a web address, the DNS servers are contacted to retrieve the DNS records of the Internet domain you are trying to reach. This way the site you'll see is going to be retrieved from the correct location. The name servers normally have a prefix “ns” or “dns” and each domain address has at least two NS records. There is absolutely no sensible difference between the two prefixes, so what type a hosting provider is going to use depends solely on their preference.