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 host company for your domain name is the easiest way to forward 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), and so forth, so if you want to change some of these records, you'll be able to do it using their system. To put it differently, 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 obtain the DNS records of the domain you are trying to reach. This way the web site that you're going to see is going to be retrieved from the proper location. The name servers normally have a prefix “ns” or “dns” and each domain has at least two NS records. There isn't any functional difference between the two prefixes, so what type a hosting provider will use depends entirely on their preference.