Microsoft Certified Systems Engineer (MCSE) Question:

An application gateway is an application program that runs on a firewall between two networks. An application gateway is used for establishing connection between client program and destination service. The client negotiates with the gateway to communicate with the service of destination. Here, gateway can be called as a proxy. Hence, two connections are made. One between client and proxy; other, between proxy and destination service. Connections take place behind the firewall