This tutorial explains how to create a Twitter SMS notification system based on tweets, retweets, and mentions using the Twilio API. The author, Charles Oduk, outlines the steps required to set up this system, including creating a Twitter developer account, setting up a Twitter app, obtaining access to the Account Activity API, and configuring the Twilio API for sending SMS notifications. The tutorial provides a step-by-step guide on how to register a webhook with Twitter that listens for specific events, such as tweets, retweets, and mentions, and sends corresponding SMS notifications using the Twilio API.