The NS, or Name Server records of a domain, indicate which servers deal with the Domain Name System (DNS) records for it. Setting the name servers of a particular host company for your domain address is the simplest way to point it to their system and all its sub-records are going to 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, in case you want to edit any one of these records, you'll be able to do it through their system. To put it differently, the NS records of a domain address reveal the DNS servers that 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 attempting to access. That way the web site that you'll see is going to be retrieved from the proper location. The name servers normally have a prefix “ns” or “dns” and every single domain address has at least 2 NS records. There is absolutely no functional difference between the two prefixes, so what kind a host company is going to use depends completely on their preference.