OPNsense is a gateway/firewall/DHCP/router my network looks like this

optical to Ethernet conversion (the isp’s things) -> opnsense box -> network switch -> all other device (including wifi APs)

all traffic gets routed thru the opnsense box as it is the gateway to my network, runs the ipv4 nat and DHCP server

router in their comment refers to the the one that actually touches the Internet