A push notification is a message that is “pushed” from backend server or application to a user interface, including (but not limited to) mobile applications and desktop programs. Users must have the application installed on their device, but need not be actively using it to receive push notifications.
Push notifications are cheaper than SMS messages while also providing more engagement value, with options for content like images, video, and rich text. When used correctly this makes them invaluable as part of a multichannel marketing campaign, as well as demonstrating the value of an app.