Moon.js is a lightweight, functional, and declarative JavaScript library designed to simplify the development of user interfaces by relying on pure functions and drivers to manage views, state, HTTP requests, and routing. The tutorial demonstrates building a blogging application using Moon.js, leveraging its HTTP driver to fetch data from the JSONPlaceholder API and display it dynamically in the browser. Moon.js supports modular development with drivers for time, storage, HTTP, and routing, enabling developers to focus on application logic while managing side effects effectively. The setup process involves installing Moon.js globally, bootstrapping a project, and integrating Tailwind CSS for styling, culminating in a functional application capable of fetching and rendering paginated data. The tutorial also highlights the importance of frontend monitoring using tools like LogRocket to ensure application performance and error tracking, emphasizing the need for visibility as frontend complexity increases with additional libraries and dependencies.