A push notification is a message that appears on a mobile device outside of an apps user interface to provide the user with reminders, communication from other people, or other timely information from the app. Push notifications are typically opt-in alerts that display text and rich media, like images or buttons, which enable a user to take a specific action. They can be sent directly to a users mobile device and can play a personalized notification tone, send users a short message, put a numbered badge over the apps icon, or enable users to complete an action without ever having to open the app.

In Android, notifications are created using the NotificationManager class, which is used to instantiate an object of this class by requesting the Android system through getSystemService() method. Once the object is created, a Notification is created through the Notification class and its attributes, such as icon, title, and time, are specified. Users can tap the notification to open the app or take an action directly from the notification.

Push notifications are important because they can help users stay engaged with an app or re-engage with an app they havent opened in a while. They are very effective at conveying messages of urgency, such as breaking news, current traffic conditions, or limited-time offers. Push notifications can be targeted to segments of an apps user base and even personalized for specific app users.

In summary, a push notification is a message that appears on a mobile device outside of an apps user interface to provide the user with reminders, communication from other people, or other timely information from the app. In Android, notifications are created using the NotificationManager class, and users can tap the notification to open the app or take an action directly from the notification. Push notifications are important because they can help users stay engaged with an app or re-engage with an app they havent opened in a while, and they can be targeted to segments of an apps user base and even personalized for specific app users.