What is Vue 3 and how does it differ from Vue 2?

Vue 3 is a full rewrite of Vue.js focused on performance, smaller bundle size, and better TypeScript support. Key differences from Vue 2:

• Reactivity: Uses ES6 Proxy instead of Object.defineProperty, enabling reactivity for property addition/deletion and array index/length changes.
• Composition API: New setup()/<script setup> style for organizing logic by feature instead of by option type.
• Multiple root nodes (Fragments): Templates no longer require a single root element.
• Teleport: Render content outside the component's DOM hierarchy.
• Suspense: Built-in support for async component trees.
• Better TS support: Rewritten in TypeScript.
• Smaller/faster: Tree-shakeable APIs and a rewritten virtual DOM with compiler-informed optimizations (patch flags).