Push notifications are messages received by mobile devices (or other computing devices). Push notifications originate from a server and are delivered to users who have installed an app and have opted-in to receive notifications from the app. Mobile users don't have to be using the app in question or even their device to receive incoming push notifications.
There are a lot of differences between SMS messaging and Push messaging, the most important one being the price difference – Push messages are a lot less expensive than SMS messages, making them the ideal communication tool for notifying app users while they are not using your app.
Push notifications can easily be enriched with various media such as images, videos, audio, and even emoji's in order to increase the open rate and offer a more engaging messaging communication.