The NS, or Name Server records of a domain, show which servers handle the Domain Name System (DNS) records for it. Setting the name servers of a particular hosting provider for your domain address is the easiest way to point it to their system and all its sub-records are going to be taken care of on their end. This includes A (the IP address of the server/website), MX (mail server), TXT (free text), SRV (services), CNAME (forwarding), etc, so if you want to change some of these records, you're going to be able to do it through their system. In other words, the NS records of a domain address show the DNS servers which 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 name you want to reach. In this way the web site that you're going to see is going to be retrieved from the right location. The name servers typically have a prefix “ns” or “dns” and each and every domain address has at least two NS records. There is no functional difference between the two prefixes, so what type a website hosting provider will use depends only on their preference.