This tutorial guides on how to build a SMS-to-Slack bridge using Python and Twilio. The bridge allows users to receive SMS messages in Slack channels and automatically forward threaded replies back as SMS messages to the original sender's phone number. To follow along, users need a free Twilio account, a free Slack account, and Python 3. The tutorial covers setting up a Flask application with Ngrok for development purposes, creating a Slack bot, and configuring Twilio to send SMS notifications. Users can test the service by sending an SMS message to their Twilio phone number and adding threaded replies in Slack.