An introductory overview of Next.js App Router routing conventions. Covers the file-based routing mental model where folders map to routes and files define UI behavior. Topics include core file conventions (page.js, layout.js, loading.js, error.js, not-found.js), nested routing, dynamic routes with square bracket syntax, route groups for code organization without URL impact, navigation hooks (useRouter, usePathname), and nested layouts for dashboards and complex apps.