Courier Push is an open-source React component that enables app-to-user communication with flexibility and customization. It allows developers to send notifications, create a notification history, and customize the user experience through modules such as Toast and Inbox. Courier Toast provides customizable notifications that can be easily integrated into web applications, while Inbox serves as a notification repository where users can access past in-app notifications. The components support customization options, including themes, render properties, and icons, enabling developers to tailor the notification experience for their specific use cases. By integrating Courier Push, developers can create effective notifications systems that cater to user preferences, leading to improved user engagement and satisfaction.