An event profiler lets you watch the event happening while you running your code and track how often and for how long they are executed.
This is useful to help you find bottlenecks in your code.
So how do you get a free event profiler?
You download JDeveloper!
And here is a little how to I wrote to get you started using the event profiler:
And by the way there are also a memory profiler and an execution profilere there for you to use.