The NS, or Name Server records of a domain name, indicate which servers manage the Domain Name System (DNS) records for it. Setting the name servers of a particular hosting provider for your domain name is the simplest 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), and so forth, so, in case you wish to modify any one of these records, you're going to be able to do it through their system. Put simply, the NS records of a domain address show the DNS servers that are authoritative for it, so when you try to open a web address, the DNS servers are contacted to obtain the DNS records of the domain name you are trying to access. In this way the website that you're going to see is going to be retrieved from the proper location. The name servers typically have a prefix “ns” or “dns” and each domain has at least two NS records. There is absolutely no practical difference between the two prefixes, so what kind a website hosting provider is going to use depends only on their preference.
