Notification without nabu casa

Hello, I wonder if someone could explain me how is it possible that I can get my notification by automation work without nabu casa subscription.
I’m not good in English but it’s working and I don’t know how. I can’t connect to my home assistant instance cause I didn’t open a port on my router.
I thing I misunderstood something… !

Thanks in advance for your time !


Édit : notification are from the android app and not from my wifi network

It uses Google Firebase. You can read more here-