NS stands for ‘name server’ and this record indicates which DNS server is authoritative for that domain (which server contains the actual DNS records).
A domain will often have multiple NS records which can indicate primary and backup name servers for that domain.
If you want to delegate a registered domain name to a different DNS provider, you can do that through the DNS Manage panel.
NB: It is important to have both NS and A record in a DNS zone if you need to delegate sub-zone to a different DNS server
Example of an NS record: