haha, this easy. Let me explain ( in fact just copied from Help file. [img]/images/graemlins/smile.gif[/img])
The 4Test Agent is the software process that translates the commands in your 4Test scripts into GUI-specific commands. In other words, it is the Agent that actually drives and monitors the application you are testing.
One Agent process can run locally on the host machine, but in a networked environment, the host machine can connect to any number of remote Agents simultaneously or sequentially.