What are Cache Components in Next.js 16?

// app/dashboard/page.tsx (with next.config.ts: { cacheComponents: true })
"use cache";

async function UserStats({ userId }: { userId: string }) {
  const stats = await fetch(`https://api.example.com/stats/${userId}`, {
    next: { tags: ['user-stats'] }
  }).then(res => res.json());
  return 
Views: {stats.views} | Sales: {stats.sales}
;
}

export default async function Dashboard({ params }: { params: Promise<{ userId: string }> }) {
  const { userId } = await params;
  return (
    <>
      <h1>Dashboard</h1>
      <Suspense fallback={<div>Loading stats...</div>}>
        <UserStats userId={userId} />
      </Suspense>
    </>
  );
}