The NS, or Name Server records of a domain name, point out which servers handle the Domain Name System (DNS) records for it. Setting the name servers of a specific hosting provider for your domain address is the most convenient way to point 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), etcetera, so, in case you need to edit any one of these records, you'll be able to do it using their system. Put simply, the NS records of a domain name reveal the DNS servers which are authoritative for it, so when you try to open a web address, the DNS servers are contacted to get the DNS records of the domain name you want to reach. In this way the web site that you're going to see is going to be retrieved from the proper location. The name servers normally have a prefix “ns” or “dns” and each domain has at least 2 NS records. There's no sensible difference between the two prefixes, so what type a hosting provider will use depends only on their preference.