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 given hosting provider for your domain is the most convenient way to forward it to their system and all its sub-records will 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), and so forth, so if you want to edit some of these records, you will be able to do it through their system. In other words, the NS records of a domain name show the DNS servers which are authoritative for it, so when you try to open a web address, the DNS servers are contacted to retrieve the DNS records of the Internet domain you are attempting to access. That way the site that you're going to see is going to be retrieved from the proper location. The name servers usually have a prefix “ns” or “dns” and each domain has at least two NS records. There isn't any sensible difference between the two prefixes, so what type a website hosting provider will use depends completely on their preference.