Send push notification messages to iOS and Google devices.
Push notifications are messages sent to an application by a central server, according to preferences defined by the user.
Production Push Notifications feature
Enables a production to send push notification messages to iOS and Google devices. This feature makes it possible to easily send notifications to a user with an application running on multiple devices. Your code can send notifications without having to be aware of the number of devices or whether the devices are iOS or Google devices. See Configuring and Using Push Notifications.