The fundamental purpose of a firewall is to establish a barrier between trusted internal networks and untrusted external networks. We may sometimes also refer to personal firewalls, which are firewalls placed on individual nodes, primarily to filter outgoing traffic. All networking firewalls have the ability to perform packet filtering, which is the ability to inspect packets and determine if they conform to the packet filter's filtering rules. If they do not match the rules, the packets will be dropped.
pfSense's firewall has three options for filtering: Pass allows the packet to pass through the firewall. Block will drop the packet silently. Reject will also cause the packet to be discarded, but a port unreachable message ...