File-system routing, Layouts, and Route Groups.
Use the App Router (app/ directory) for all new projects.
(auth) to organize routes without affecting URL path.
app/(auth)/login/page.tsx -> /login_lib to exclude folders from routing.[slug].
app/blog/[slug]/page.tsx -> /blog/abc[...slug] matches subsequent segments.<Link href="/dashboard"> for prefetching.useRouter hook (Client Components only).
router.push('/dashboard')redirect('/login') in Server Components.app/layout.tsx) for <html> and <body> tags.