I'm a pfSense newbe, but I know networking in general.
On your WAN side you'll have one of your static IPs assigned to pfSense, along with the /28 to tell it the size of your subnet, and the gateway address (the address of your modem).
My ancient SonicWALL was just smart enough to be stupid. It knew the 0th, 15th, gateway, and it's own address were unavailable, and so the other 12 addresses in that /28 subnet must belong on the LAN–so it set itself to bridging mode (you could override that with NAT if desired).
pfSense is much smarter than that and so it assumes nothing. What if there were other hosts between it and the gateway? Therefore you must set virtual IPs to tell it that when it sees one of them, it must do something with it. There is a bridging mode in pfSense, but my neighbor suggested 1-to-1 NAT would be better. Or one could use port forwarding, in which case rules can be auto-generated. Three choices, but all require virtual IPs be set first.
To set virtual IPs go to "Firewall / Virtual IPs".
It's a little hard to find bridging in the GUI, so here's a page in the DOCs that describes it. https://doc.pfsense.org/index.php/Interface_Bridges