In React (ES6), why do I *sometimes* see this?...

```
class Hello extends React.Component { ... }

```

and sometimes *this*?

```
export class Hello extends React.Component { ... }

```

What is the significance of the `export` keyword? If using webpack, would this require any changes to the webpack.config.js file?

Any info on this would be appreciated, thanks in advance.

---

UPDATE:

**main-file.js**

```
import React from 'react';
import ReactDOM from 'react-dom';

import { External } from './external';

class Hello extends React.Component {
  render() {
    return <div>

      <h1>Hello World (Main File this time)</h1>
      <External />

    </div>
  }
}

ReactDOM.render(<Hello/>, document.getElementById('main'));

```

**external.js** (same directory)

```
export class External extends React.Component {
  render() {
    return <div>This is my external component</div>
  }
}

```

This doesn't work - can you see why??