The NS, or Name Server records of a domain, show which servers deal with the Domain Name System (DNS) records for it. Setting the name servers of a particular hosting provider for your domain address is the most convenient way to forward 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), etc, if you need to change any of these records, you'll be able to do it 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 try to open a web address, the DNS servers are contacted to retrieve the DNS records of the domain name you are attempting to reach. In this way the web site that you'll see is going to be retrieved from the right location. The name servers normally have a prefix “ns” or “dns” and each and every domain name has at least two NS records. There is absolutely no sensible difference between the two prefixes, so which one a hosting provider will use depends exclusively on their preference.