This tutorial provides a comprehensive guide on building a chat application using PubNub's AngularJS SDK, focusing on implementing features like infinite scroll, message storage, and real-time communication. It emphasizes best practices for structuring an AngularJS app, such as creating a dedicated Message Service to handle message storage and retrieval, and utilizing a UI split into reusable components for improved maintainability and scalability. The guide details the configuration of PubNub for real-time message handling and explores techniques like using AngularJS directives and Lodash for enhanced user experience features such as auto-scrolling and fetching previous messages upon scrolling to the top. It also includes methods to improve performance with techniques like track-by in ng-repeat and throttling scroll events, while providing code snippets and examples to illustrate the implementation process.