A NS Record tells recursive name servers which name servers are authoritive for a zone. These nameservers look at the NS records to figure out who to ask when resolving a name. They are the supporting layer for the domain name system and as such, are stored in in the DNS zone files.

As such they identify the name of both the primary and secondary DNS servers that are responsible for a zone and they're responsible for DNS resolution of a specific domain. Because of this every DNS zone must have a dedicated NS record assigned to it.

In practice this means that when a user switches to a new hosting provider, the NS records need to be changed so that visitors can reach that user’s website. This can take up to 24 hours because the NS records change needs to be propagated across the Internet.

For this reason, web hosts and domain registrars allow their clients to edit the NS records for their domain and it's the most basic functionality of domain names because, without it, the internet won’t function properly, and visitors won't be able to find a domain through their browser.

It's important to keep in mind that the role of NS records is limited because they only serve to define the name of the domain and they don't include the IP addresses that will make sure that a domain resolution request succeeds.

For this reason, administrators need to assign an IP address with an A record to the NS records for their specific DNS servers. In doing so, they ensure that a connection can be established to these servers so that a DNS resolution can take place.