This tutorial demonstrates how to send SMS messages from a Google Spreadsheet using Apps Script and Twilio's Messaging API. The process involves creating a new spreadsheet with columns for phone numbers, message bodies, and status, then writing code to read data from the spreadsheet and send an HTTP POST request to the Twilio API with the phone number and message body as parameters. Once the script is set up, it can be run to send SMS messages to the specified phone numbers in the spreadsheet. The tutorial also touches on additional functionality, such as validating phone numbers and accessing more advanced features of the Messaging API.