rephrased a bit to be more clear but feel free to edit

"At the beginning of the file there is a +onNotification+ function, which acts as a central hub invoked by the Cordova PushPlugin when it is time to deliver an interesting event to the application. The events we are mostly interested to utilise are the 'registered' and 'message'. The former is invoked when the PushPlugin has successfully registered the device with the GCM service, so we get the chance to register the device with the UnifiedPush server. This is done by calling 'app.registerDevice(e.regid)' function passing along the device token received by the CGM (more details on the function later in the tutorial).