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 is the most effective way to direct 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, so if you need to edit any one of these records, you will be able to do it by using their system. To put it differently, the NS records of a domain address point out the DNS servers that are authoritative for it, so when you attempt to open a web address, the DNS servers are contacted to get the DNS records of the Internet domain you are trying to access. In this way the site that you're going to see is going to be retrieved from the right location. The name servers normally have a prefix “ns” or “dns” and each domain name has at least 2 NS records. There's no sensible difference between the two prefixes, so which one a web hosting provider is going to use depends completely on their preference.