That is the relevant information. You are using Ionic Native. (I fixed your topic’s category)
Ionic Native Push is “only” a convenient wrapper around the Cordova plugin. Here is the documentation on init and its options:
https://github.com/phonegap/phonegap-plugin-push/blob/master/docs/API.md#pushnotificationinitoptions
To be honest this is not much more real “explanation” than you gave yourself, but that is mainly because there isn’t more to tell. You tell the plugin to do it’s job with some parameters, it returns the data you need to work further with it (registrationId to send push via API of your push provider).