When you add and configure an Event Monitor tool, the events reported by Event Monitor will be reported to the Event Details perspective as well—as long as you run a Test Configuration with event logging enabled (as described above).
When you use Event Monitor tools in concert with the Event Details perspective, you have multiple event monitors and multiple tests. The various events that they report (traffic sent/received, some inter-mediate message picked up on a JMS topic, failure, etc.) will all be logged chronologically into the Event Details log. This gives you a central location for analyzing actions taking place in SOAtest and the corresponding actions that occur in the system under test—possibly from multiple different components (sources) in the system under test.