first of all next time when you have a question you should post it as discussion not a document
regarding your topology, it is high level topology dose not show detailed connections, however it is clear that these firewalls are working in active/standby mode and they are placed in DMZ or security zone to protect some networks where traffic in and out to this secured network has to go via the firewall
hope this help
Getting Started
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: