The NS, or Name Server records of a domain name, show which servers handle the Domain Name System (DNS) records for it. Setting the name servers of a specific 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, if you want to modify any one of these records, you're going to be able to do it by using their system. Put simply, the NS records of a domain address show the DNS servers that are authoritative for it, so when you attempt to open a web address, the DNS servers are contacted to retrieve the DNS records of the domain you want to access. That way the site that you will see is going to be retrieved from the proper location. The name servers normally have a prefix “ns” or “dns” and each and every domain name has at least two NS records. There isn't any functional difference between the two prefixes, so which one a host company is going to use depends exclusively on their preference.