The NS, or Name Server records of a domain, reveal which servers deal with the Domain Name System (DNS) records for it. Setting the name servers of a specific host company for your domain name is the most effective way to direct it to their system and all its sub-records will 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), etcetera, if you want to modify some of these records, you're going to be able to do it through their system. In other words, 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 are trying to reach. That way the site that you're going to see will be retrieved from the right location. The name servers usually have a prefix “ns” or “dns” and every single domain name has at least two NS records. There is no practical difference between the two prefixes, so what kind a hosting provider will use depends exclusively on their preference.