This tutorial demonstrates how to build a serverless application using the Chalice framework that invokes the Nexmo Voice API to play a message, ask for user input, and then send a callback with the result of the interaction. The application is deployed on AWS Lambda and uses DynamoDB to store call state information. The process involves deploying the function to AWS, setting up authentication using either private key or JWT authentication methods, and invoking the function with parameters such as the number to be called, initial message, PIN code, callback URL, and callback method. After the call is completed, the Lambda function makes a callback request to a webhook specified during invocation, containing details of the call and result. The application provides flexibility in handling user input, retries, and error messages, allowing developers to customize their implementation as needed.