React is a library, Next.js is a framework

In the React course you built components. React draws the screen, but it leaves other jobs to you: giving each page its own URL, loading data, and preparing the app for real visitors.

Next.js is a framework built on React. A framework is a set of tools and rules that already answers those questions. You write components and follow its file layout.

Routing. Each folder you create becomes a URL.
Server rendering. The server builds the HTML before it sends the page.
Data fetching. A component can load its data on the server.
Build. One command prepares a production version of the app.

app/page.tsx

export default function Home() {
  return <h1>Hello, Next.js!</h1>;
}

export default function Home() {
  return <h1>Hello, Next.js!</h1>;
}

This code needs a server, so it is not run here. Check looks for the right pieces. Try it for real in your own project.