This is also referred to as the “Proxy”.
Proxies handle web based traffic, and the core function is at Layer 7 on the OSI Model
The proxy focuses on inspecting and modifying HTTP/HTTPS. Think websites, SSL certificates etc.
Usually, when users have issues with accessing a website and isnt getting blocked by the firewall, it is likely the proxy that is causing the issue.
Helpful knowledge here is knowing “SSL Bypass” “Content Filtering”