The NS, or Name Server records of a domain, point out 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 most convenient way to point it to their system and all its sub-records are going to be managed 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 of these records, you're going to be able to do it using their system. To put it differently, the NS records of a domain point out the DNS servers that are authoritative for it, so when you attempt to open a web address, the DNS servers are contacted to get the DNS records of the Internet domain you are attempting to reach. That way the website that you'll see is going to be retrieved from the right location. The name servers typically have a prefix “ns” or “dns” and each domain address has at least 2 NS records. There is absolutely no sensible difference between the two prefixes, so which one a host company is going to use depends entirely on their preference.