Summary of "How React ACTUALLY works (DEEP DIVE 2023)"

The subtitles from the YouTube video provide a deep dive into how React works. React is described as a library, not a framework, that allows building user interfaces using components. React reacts to changes in data using State, updating the UI accordingly. The video explains how to add React to an HTML page, the use of JSX to describe UI elements, and the rendering process in React. It also delves into the trigger, render, and commit steps in updating the UI, the use of virtual DOM for performance, and the importance of keys in React elements for efficient rendering. The video highlights the benefits and challenges of using JSX, the role of State in React components, and the performance optimizations made by React. The speaker provides detailed explanations and examples throughout the video.