The GitHub Action uses Python and the Twilio service to send SMS notifications about pull requests or issues in a repository. The action is defined using a YAML file, which includes inputs for customizing the notification settings. The action runs inside a Docker container, with a Dockerfile that specifies the Python environment and dependencies. After setting up the development environment, getting a Twilio phone number, and building the action, the workflow file is configured to run the action on a repository, sending an SMS when a pull request or issue is opened or closed. The action can be customized using inputs, and it includes a Dockerfile and an action.yml file for defining the action's behavior.