The NS, or Name Server records of a domain name, show which servers manage the Domain Name System (DNS) records for it. Setting the name servers of a specific hosting provider for your domain address is the most convenient way to direct it to their system and all its sub-records are going to be taken care of 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 if you wish to modify any one of these records, you're going to be able to do it through their system. In other words, the NS records of a domain show the DNS servers that are authoritative for it, so when you try to open a web address, the DNS servers are contacted to retrieve the DNS records of the domain you want to access. This way the web site that you will see is going to be retrieved from the correct location. The name servers typically have a prefix “ns” or “dns” and each domain address has at least 2 NS records. There isn't any practical difference between the two prefixes, so which one a host company will use depends exclusively on their preference.