A React application is built from components. A component is a reusable piece of the user interface that controls what appears on the screen. Instead of building an entire page as one large block, React encourages you to split the interface into smaller parts. Each part is responsible for a specific section of the UI, such as a header, a button, or a message.

In React, components are written using JavaScript and defined as functions. Each component returns a description of what should appear on the screen, and React takes care of displaying it.

Components make interfaces easier to understand and maintain. When the UI grows, components help you organize code, reuse logic, and avoid repetition. Below is a simple example of a React component:

function Welcome() {
  return <h1>Welcome to React</h1>;
}

This is a React component called Welcome. It returns a UI element that React can render on the screen. You do not need to understand the syntax yet. This example is here to show what a component looks like at a high level.