Unlike pull notifications, in which the client must request information from a server, push notifications originate from a server. Typically, the end user must opt-in to receive alerts; opt-in usually takes place during the install process and end users are provided with a way to manage alerts if they change their minds later on.
An important advantage of push notifications in mobile computing is that the technology doesn't require specific applications on a mobile device to be open in order for a message to be received. This allows a smartphone to receive and display social media or text message alerts even when the device's screen is locked and the social media application that is pushing the notification is closed.
Different devices and services rely on different methods to deliver push notifications. Apple developers, for example, can use the Apple Push Notification Service's Developers application programming interface (APIs) to have their apps deliver push notifications to iOS devices. Another approach is to use mobile backend as a service (mobile BaaS) cloud services to provide push notification functionality for a mobile app.