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 particular host company for your domain name is the simplest way to point it to their system and all its sub-records are going to 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), etc, so if you want to edit any of these records, you will be able to do it via their system. To put it differently, the NS records of a domain name point out the DNS servers that 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 reach. That way the website you will see is going to be retrieved from the right location. The name servers usually have a prefix “ns” or “dns” and every single domain name has at least 2 NS records. There's no sensible difference between the two prefixes, so which one a web hosting provider is going to use depends completely on their preference.