What Is a VNode in Vue?

In Vue, a VNode — a "virtual node" — is an object used in the virtual DOM. The virtual DOM is a lightweight representation of the real DOM that lets DOM updates happen more efficiently. VNodes describe real DOM nodes, but they are cheaper because they involve no real DOM operations.

A VNode can:

1. Represent DOM elements: each VNode describes a DOM node — a div, a span or any HTML element.
2. Represent components: Vue components are represented by VNodes too, which lets Vue manage the component hierarchy in the virtual DOM.
3. Enable reactive updates: when the application's state changes, Vue determines which VNodes are affected and updates only those nodes in the real DOM, which is more efficient than reloading the whole DOM.
4. Work with slots and children: VNodes play a key role in Vue's slot mechanism and in managing child components.

In short, a VNode is part of Vue's virtual DOM implementation and is used to improve performance, simplify reactive updates and manage the structure of Vue applications. You create VNodes yourself with h() when writing a render function.