What is Virtual DOM and what is it used for?

Virtual DOM is an abstraction of the real DOM, representing a lightweight copy of the user interface structure in memory. It is used to optimize interface updates: instead of directly modifying the real DOM, which is resource-intensive, changes are first applied to the Virtual DOM. Then, using a diffing algorithm, the minimal set of changes needed to update the real DOM is calculated, significantly improving application performance and responsiveness.

Example: in React, when the state of a component changes, a new Virtual DOM is created, compared with the previous one, and only the changed elements are updated in the real DOM.