The NS, or Name Server records of a domain, reveal which servers manage 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 taken care of on their end. This includes A (the IP address of the server/website), MX (mail server), TXT (free text), SRV (services), CNAME (forwarding), etc, if you need to change any of these records, you're going to be able to do it through their system. Put simply, the NS records of a domain address point out 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 Internet domain you are attempting to access. This way the web site that you will see is going to be retrieved from the right location. The name servers normally have a prefix “ns” or “dns” and each domain has at least two NS records. There isn't any practical difference between the two prefixes, so what kind a host company will use depends solely on their preference.