What is React?

React is a JavaScript library for building user interfaces. Created by Facebook in 2013, it has become the most popular front-end library in the world.

React introduces a component-based architecture. Instead of writing a monolithic HTML page, you break your UI into small, reusable pieces called components. Each component manages its own logic and appearance.

Why React?

React makes it easy to build complex, interactive UIs. It uses a virtual DOM to efficiently update only the parts of the page that actually change, making it blazing fast.

React also has an enormous ecosystem — React Router for navigation, Redux for state, Next.js for full-stack apps, and thousands of UI libraries.

Your First Component

Here is the simplest React component you can write:

function Hello() { return <h1>Hello, World!</h1> }

This is a function that returns JSX — a syntax that looks like HTML but is actually JavaScript.