Twilio is a service that allows developers to control and interact with phone calls programmatically. This article shows how to use Twilio, Java, and Google Sheets to take control of incoming calls, screen them, and treat them differently based on who's calling. The code uses Spring Boot as the web application framework and handles incoming calls by fetching caller information from a Google Sheet, looking up an action in the sheet, and generating TwiML (Twilio Markup Language) that determines how to handle the call. The article provides step-by-step instructions for setting up the project, creating a Google Sheet, enabling Google Sheets API access, testing the setup, and using a local app for Twilio webhooks.