What is Virtual DOM ?

The virtual DOM (VDOM) is a programming concept where an ideal, or virtual, representation of a UI is kept in memory and synced with the real DOM by a library such as ReactDOM. This process is called reconciliation.

This approach enables the declarative API of React: You tell React what state you want the UI to be in, and it makes sure the DOM matches that state. This abstracts out the attribute manipulation, event handling, and manual DOM updating that you would otherwise have to use to build your app.

Since virtual DOM is more of a pattern than a specific technology, people sometimes say it to mean different things. In React world, the term virtual DOM is usually associated with React elements since they are the objects representing the user interface. React, however, also uses internal objects called fibers to hold additional information about the component tree. They may also be considered a part of virtual DOM implementation in React.