App notifications are messages sent by applications on your smartphone or device to inform you about updates, reminders, or new content. They can appear as banners, alerts, or badges, and are designed to grab your attention without needing to open the app. Notifications help users stay engaged and informed about important events or changes. Users can customize their app notifications by adjusting settings within each application or through their device's notification settings. This allows individuals to choose which notifications they want to receive and how they want to be alerted, ensuring a more personalized experience with their apps.