firewalld is based on iptable and therefore is based on the same concept such as:
- zone - trust level on Network interfaces and source,
- rule - traffic rules
- policy - traffic rules between zones if you happen to have more than one interface.
Firewalld is the default firewall on most Linux distributions (Fedora 38, Centos 7, …)
This how to page is a cheatsheet page that lists the major command. You will find howto's such as country or subnet filtering around firewalld.