2. **Two Phases of Rendering**

A. Render Phase (work-in-progress)

• React builds a work-in-progress Fiber tree.
• It walks through each component (begin phase), calculates what needs to change, and collects side effects (complete phase).
• This phase is interruptible—React can pause it and resume later.

B. Commit Phase

• React applies changes to the Real DOM.
• Runs lifecycle methods (e.g., componentDidMount, useEffect).
• This phase is non-interruptible but fast.