when will RELEASESTEPCREATED event trigger for PO workflow

Hi,

i am working on PO  release workflow by implementing custom worklfow using user decision step.

when will RELEASESTEPCREATED event gets triggerd ?

RELEASESTEPCREATED event triggers only  based on release stratagy maintained in the configuartion in SPRO?

                                              or

RELEASESTEPCREATED event triggers for every new creation of PO in system ?

please clarify when that event will trigger .

Thanks,

Phani