The NS, or Name Server records of a domain, indicate which servers manage the Domain Name System (DNS) records for it. Setting the name servers of a particular hosting provider for your domain is the most effective 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), etcetera, so, in case you wish to change any one of these records, you will be able to do it by using their system. Put simply, the NS records of a domain name point out 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 domain you are attempting to access. In this way the web site you'll see is going to be retrieved from the right location. The name servers normally have a prefix “ns” or “dns” and each domain has at least 2 NS records. There isn't any functional difference between the two prefixes, so which one a hosting provider will use depends solely on their preference.