The NS, or Name Server records of a domain, reveal which servers handle the Domain Name System (DNS) records for it. Setting the name servers of a specific hosting provider for your domain address is the easiest way to forward it to their system and all its sub-records will 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 on, so, in case you want to change any one of these records, you are going to be able to do it using their system. Put simply, the NS records of a domain name reveal the DNS servers which 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. This way the site that you'll see is going to be retrieved from the right location. The name servers typically have a prefix “ns” or “dns” and every single domain has at least 2 NS records. There isn't any practical difference between the two prefixes, so which one a website hosting provider is going to use depends completely on their preference.