Can you walk me through how React updates the screen efficiently?

The Virtual DOM (VDOM) is a programming concept where a virtual representation of the UI is kept in memory and synced with the real DOM through a process called reconciliation. React creates a virtual DOM tree that mirrors the structure of your actual DOM elements.

When state changes in a React component, React first updates the virtual DOM rather than the real DOM directly. It then compares the new virtual DOM with the previous version using a diffing algorithm. This comparison identifies exactly which parts of the UI need to change.

Only the differences (or "diffs") are then applied to the real DOM in a process called reconciliation. This batched, minimal update approach is much more efficient than directly manipulating the DOM for every change, as DOM operations are computationally expensive.

The key benefits include: improved performance through batched updates, a declarative API that abstracts away direct DOM manipulation, and cross-platform capability since the virtual DOM concept works beyond just web browsers (e.g., React Native).