The NS, or Name Server records of a domain, indicate 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 simplest way to direct 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), and so forth, so if you would like to change any of these records, you're going to be able to do it by using their system. Put simply, the NS records of a domain name 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. This way the site that you'll see will be retrieved from the proper location. The name servers normally have a prefix “ns” or “dns” and every single domain address has at least two NS records. There's no sensible difference between the two prefixes, so which one a host company is going to use depends exclusively on their preference.