Push notifications are messages sent directly to a user's device from an app or website. They appear on the screen even when the app is not actively in use, providing timely updates or alerts. These notifications can include reminders, news updates, or promotional offers, helping to keep users engaged with the content. Users can customize their preferences for push notifications, choosing which apps can send them and how often. This feature allows for a more personalized experience, ensuring that users receive information that is relevant to their interests without being overwhelmed by excessive alerts.