What is the virtual DOM in React?

The Virtual DOM in React is an abstraction of the real DOM, representing a lightweight tree of objects in memory that reflects the UI structure. When the component's state changes, React first updates the virtual DOM, then compares the new tree with the previous one (a process called "reconciliation"). After that, React calculates the minimal set of changes (diff) and applies them to the real DOM, significantly improving performance since manipulations with the real DOM are costly operations.

It roughly looks like this:

// React updates the virtual DOM
const newVDOM = <div>{state.value}</div>;
// React compares with the previous virtual DOM
// and updates only the changed parts in the real DOM

Thus, the virtual DOM allows efficient management of interface updates, minimizing the number of operations with the real DOM.