This tutorial demonstrates how to implement One Time Password (OTP) login and signup functionality in a Yii 2 PHP application using Twilio SMS. The application allows users to sign up with their phone number, receive an OTP via SMS, and log in using the OTP. The system ensures that only valid phone numbers are accepted and provides a secure way for users to authenticate themselves. The code is well-structured, and the tutorial covers essential aspects of implementing OTP authentication, including setting up models, controllers, and views.