React's Virtual DOM is a method used to enhance web application performance by creating a lightweight, in-memory representation of the user interface, thus avoiding unnecessary updates to the actual Document Object Model (DOM). This technique, employed by many JavaScript frameworks like React, Angular, and Vue.js, significantly reduces the load on web applications by ensuring that only the parts of the DOM that have changed are updated, rather than re-rendering the entire DOM. In contrast to the Core DOM, which updates entirely with every change, the Virtual DOM performs a diffing process to compare new and previous versions and only updates the necessary elements. This approach enhances user experience by reducing latency and preserving the state of interface elements, like input fields, during re-renders. It also optimizes CPU and memory usage, making applications faster and more efficient. React utilizes the Virtual DOM through a process called reconciliation, managed by ReactDOM, which efficiently syncs the virtual representations with the real DOM. Automated testing frameworks, such as Jasmine, can be used alongside cloud-based testing platforms like LambdaTest to ensure the web application's performance remains optimal across different browsers and operating systems.