Why does my server have separate zone files for hostname and nameservers?

Question

Why does my server have separate zone files for hostname and nameservers?

Answer 

By default, cPanel creates zone files for the system hostname and nameserver names during the initial setup, since the zone file for the root domain doesn't exist on the server. If the account for the root domain is later added to the server, there will also be a zone file for the root domain.