Hi Luiz, Growl is basically an unified notifier board for Apple's OS X, that various software including Photo Mechanic can use to post visible messages to the user even if the software itself is hidden or out of view. The main feature in connection with PM is the ingest, when you are ingesting a card you can switch to another application like Safari or Mail, continue your work, and when the ingest finishes in the background, PM will tell Growl and Growl will display a simple notification pop up in a corner of the screen (configurable in many ways like which corner, duration, colours, et cetera). Which is pretty nice because you can continue working on the computer during the ingest, in other apps, but you get instantly notified when the ingest finishes. I am not sure if other features of PM like FTP upload are Growl integrated as well, but I do use it for ingesting. PM does have its own notify system I think, but Growl has been an already used standard for such things, and works pretty well for that, so I am glad they included the support for it in PM. And it used to be free (the older version is still free, but newest on Apple App store is like 1.99$ I think).
All in all, a nice thing to have, but nothing you couldn't get without. But for the ingest, the notifications are pretty nice.
