The NS, or Name Server records of a domain name, indicate which servers deal with the Domain Name System (DNS) records for it. Setting the name servers of a particular hosting provider for your domain is the easiest way to direct 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, if you wish to change any one of these records, you're going to be able to do it by using 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 try to open a web address, the DNS servers are contacted to get the DNS records of the domain name you are trying to access. That way the site you'll see will be retrieved from the right location. The name servers usually have a prefix “ns” or “dns” and each domain has at least 2 NS records. There is no practical difference between the two prefixes, so which one a hosting provider is going to use depends exclusively on their preference.