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 given host company for your domain is the easiest 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), etc, if you need to modify some of these records, you will be able to do it using their system. To put it differently, the NS records of a domain name reveal the DNS servers which are authoritative for it, so when you try to open a web address, the DNS servers are contacted to get the DNS records of the domain name you are attempting to access. In this way the web 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 each and every domain name has at least two NS records. There is absolutely no sensible difference between the two prefixes, so what type a hosting provider is going to use depends entirely on their preference.