This tutorial demonstrates how to use Twilio's Programmable Voice and SMS APIs to send a text message during a phone call using Node.js and Express. The app accepts an incoming call, says something to the caller, and sends a follow-up text message with a secret password. To handle exceptions when sending an SMS to landline numbers, the app includes error handling to print the error message and continue playing the voice response. The tutorial covers setting up a development environment, creating an Express application, handling incoming calls, sending SMS replies, and implementing exception handling for landlines.