The NS, or Name Server records of a domain name, reveal which servers manage the Domain Name System (DNS) records for it. Setting the name servers of a particular host company for your domain is the easiest way to point 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), and so on, so, in case you want to modify any one of these records, you are going to be able to do it via their system. Put simply, the NS records of a domain reveal the DNS servers that are authoritative for it, so when you try to open a web address, the DNS servers are contacted to obtain the DNS records of the domain you are trying to reach. This way the website that you'll see is going to be retrieved from the correct location. The name servers usually have a prefix “ns” or “dns” and each and every domain has at least two NS records. There is no sensible difference between the two prefixes, so which one a hosting provider is going to use depends completely on their preference.