what is the App Store server used for

The App Store server is used for several key functions related to in-app purchases. Here are the main uses:

Querying Transaction Information: The App Store server API allows you to make requests from your server to the App Store server to obtain information about transactions, such as a customer's transaction history. This can help you manage and track purchases more effectively.
Handling Refunds and Customer Satisfaction: The API includes endpoints related to refunds, allowing you to send consumption information to participate in the refund decisioning process.
App Store Server Notifications: These notifications allow the App Store to proactively inform your server of transaction updates, such as upgrades, renewals, and refunds. This helps ensure that your server is always up-to-date with the latest transaction information.
Content Delivery: Your server is responsible for granting content to users after a purchase. It should be the sole source of truth for what your customers have access to, ensuring that content is granted correctly and securely.
Promotional Offers: The App Store server library provides a simple way to create promotional offer signatures, making it easier to manage special offers and discounts.
Transition from Deprecated Endpoints: The App Store server library helps in transitioning away from deprecated endpoints like the verify receipt endpoint, providing a more robust and secure way to handle transactions.

For more detailed information, you can refer to the session Explore App Store server APIs for In-App Purchase.