A firewall alias is a user-defined label used in firewall configurations to represent a group of IP addresses, MAC addresses, or network ports. Instead of specifying each address or port individually in firewall rules, administrators can use aliases to simplify rule management and improve readability. For example, an alias named 'Office_Networks' could include multiple internal IP ranges, allowing a single rule to apply to all of them. Aliases make it easier to update firewall policies, as changes to the group only need to be made in one place. This reduces errors and administrative overhead, especially in complex network environments.