What Is React and Why Components Matter

Site Admin · 11 Sep 2026 · 12 views

What Is React and Why Components Matter

React is a JavaScript library, created by Meta, for building user interfaces. It is not a full framework. React focuses on one job: rendering the view layer of your application, usually inside a single page that updates fast without reloading.

The component model

Everything in React is a component. A component is a small, reusable piece of UI that owns its own markup, logic, and styling. You compose many small components to build a large screen, just like assembling a page from building blocks. This keeps code organized, testable, and easy to maintain.

A tiny component

Components are just functions that return markup. Here is the classic example:

function Greeting() {
  return <h1>Hello, world!</h1>;
}

export default Greeting;

The function returns JSX, which looks like HTML but lives inside JavaScript. When rendered, React turns that JSX into real DOM elements on the page.

Why components over plain HTML

With plain HTML you repeat the same markup everywhere it appears. With components you write it once and reuse it. If the design changes, you update one place. Components also receive data through props and manage their own local state, which makes each piece of the UI self-contained.

React vs. other approaches

React updates only what changed using a Virtual DOM. When state changes, React re-renders the affected components and applies the smallest set of changes to the real DOM. That gives snappy, efficient updates even on complex pages.