The NS, or Name Server records of a domain, show which servers deal with the Domain Name System (DNS) records for it. Setting the name servers of a given host company for your domain name is the most effective 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), etc, so, in case you wish to edit any of these records, you're going to be able to do it by using their system. To put it differently, the NS records of a domain show the DNS servers that are authoritative for it, so when you try to open a web address, the DNS servers are contacted to get the DNS records of the domain name you are attempting to access. This way the website you'll see will be retrieved from the correct location. The name servers typically have a prefix “ns” or “dns” and every single domain name has at least 2 NS records. There isn't any sensible difference between the two prefixes, so which one a hosting provider is going to use depends only on their preference.