It is a lightweight in-memory representation of the actual DOM to track changes in the UI and efficiently update the real DOM when necessary. 
- When there are changes in a React component, instead of directly manipulating the real DOM, React creates a virtual representation of the changes in memory and then calculates the most efficient way to update the real DOM. This approach minimizes direct manipulation of the DOM, leading to improved performance.
 - React's Virtual DOM is a key to its performance optimization. It's an abstraction of the actual HTML DOM. 
 - React's Virtual DOM acts as an intermediary layer between your React components and the actual browser DOM.