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 Vue.js. It works by keeping a virtual copy of the DOM tree in memory, which is then used to compare against the real DOM. Whenever a change is made to the DOM, the VDOM will compare the changes to the virtual DOM and only update the actual DOM with the necessary changes. This helps to optimize performance and reduce the amount of time it takes to update the DOM.
For example, in Vue.js, when a component is updated, the VDOM will compare the virtual DOM to the actual DOM and only update the actual DOM with the changes that were made. This helps to optimize performance and prevent unnecessary updates to the DOM.