What means Push Notification?
Push notifications let your application notify a user of new messages or events even when the user is not actively using your application.
On Android devices, when a device receives a push notification, your application's icon and a message appear in the status bar.
When the user taps the notification, they are sent to your application.
Notifications can be sent to all users, such as for a marketing campaign..
Admin demo: http://demo11.oc-extensions.com/modules/admin/ (user: demo, password: demo)
Help here: http://www.oc-extensions.com/Android-Store-Opencart-2.x (see tab Help)
IMPORTANT: Push Notification require to upload APK to Google Play (to register as developer)