The DNS resolver allows pfSense to resolve DNS requests using hostnames obtained by the DHCP service, statically obtained DHCP mappings, or manually obtained information. The DNS resolver can also forward all DNS requests for a particular domain to a server specified manually.
Prior to pfSense Version 2.2, DNS forwarder was the default DNS server for pfSense. Version 2.2 and later iterations use Unbound (DNS resolver) as the default DNS server; however, DNS forwarder is still available.