The NS, or Name Server records of a domain, reveal 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 direct 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), etc, so, in case you need to modify some of these records, you're going to be able to do it through their system. To put it differently, the NS records of a domain reveal 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 name you want to access. That way the site you'll see is going to be retrieved from the correct location. The name servers usually have a prefix “ns” or “dns” and each domain address has at least two NS records. There isn't any functional difference between the two prefixes, so what type a website hosting provider will use depends solely on their preference.