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 particular host company for your domain is the easiest 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), etc, so if you need to change any one of these records, you are going to be able to do it through their system. Put simply, the NS records of a domain address reveal the DNS servers which 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 domain name you are trying to access. That way the site that you're going to see will be retrieved from the correct location. The name servers usually have a prefix “ns” or “dns” and every single domain name has at least 2 NS records. There isn't any functional difference between the two prefixes, so what type a hosting provider will use depends exclusively on their preference.