The Go web application in this tutorial leverages the Twilio Voice API to make automated phone calls and play pre-recorded audio files. The application consists of a main function that serves the index file and handles incoming requests, as well as a callHandler function that validates user input, makes the phone call using the Twilio API, and returns the response to the client. The application uses environment variables to store sensitive information such as account SID and auth token, and uses Bootstrap for styling and JavaScript functions to validate form submissions and handle server responses. By following this tutorial, developers can create their own automated phone calling applications with Twilio Voice and Go.