Types of Firewall Technologies:
Cisco breaks firewall technologies down into two types. There are IOS devices that perform security and firewall services. Then, there are specific devices dedicated to being a firewall, which is purposely designed for security. IOS devices are generally routers, with the proper security version or licensed operating system to be able to perform security tasks. They can use access lists to help filter traffic from coming in or going out of the device. They can also be implemented as a zone based firewall, using zone pairs to filter traffic.
Cisco Firewall Technologies: A Guide For Beginners