The NS, or Name Server records of a domain name, reveal which servers handle the Domain Name System (DNS) records for it. Setting the name servers of a specific host company for your domain name is the most convenient way to point 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 need to change any one of these records, you're going to be able to do it via their system. Put simply, the NS records of a domain name show the DNS servers that are authoritative for it, so when you attempt to open a web address, the DNS servers are contacted to obtain the DNS records of the Internet domain you are trying to reach. This way the website that you're going to see is going to be retrieved from the right location. The name servers normally have a prefix “ns” or “dns” and each and every domain name has at least two NS records. There's no sensible difference between the two prefixes, so what kind a hosting provider will use depends completely on their preference.