The tutorial outlines a comprehensive guide on setting up a user authentication system using the Sync Gateway API, Node.js, and an Android application. It explains the process of client-side authentication to replicate user-accessible data, emphasizing the necessity of pre-existing users in the Sync Gateway database for basic authentication. The guide details how to create users through the Admin REST API and configure an app server with Node.js using the Express module to handle user sign-ups, with all other traffic proxied to Sync Gateway. Further, it describes the development of a simple Android app using Android Studio, incorporating Material Design components and OkHttp for HTTP requests, to test the sign-up and login functionalities. The tutorial concludes by demonstrating how to implement user login and sign-up screens and manage HTTP requests, ensuring a seamless authentication process with status code feedback via Toast messages in the app.