This tutorial aims to create a voicemail service using Twilio Voice and ASP.NET Core. The project involves setting up an Interactive Voice Response (IVR) app that records and serves voicemails, managing them by calling the Twilio phone number. The system consists of three main controllers: IncomingCall, Record, and Directory. The Record controller handles the recording process, while the Directory controller plays back messages to the caller and allows them to save or delete recordings. The FileService class is responsible for storing and retrieving voicemails from the file system. The application uses TwiML instructions to manage calls and send HTTP requests between the web API and Twilio. The tutorial covers setting up the project, implementing the IVR app, and testing the application.