The NS, or Name Server records of a domain, indicate which servers handle the Domain Name System (DNS) records for it. Setting the name servers of a particular hosting provider for your domain name 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), and so forth, so if you need to change any one of these records, you will be able to do it through their system. To put it differently, the NS records of a domain name show the DNS servers that 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 Internet domain you are trying to access. That way the web site you'll see will be retrieved from the right location. The name servers normally have a prefix “ns” or “dns” and each and every domain address has at least two NS records. There isn't any functional difference between the two prefixes, so which one a website hosting provider will use depends only on their preference.