Next.js App Router Mastery

Core Concepts

1. Server Components by Default - Components are server-rendered unless marked 'use client'
2. Streaming & Suspense - Progressive rendering with loading states
3. Parallel Routes - Simultaneous route rendering
4. Intercepting Routes - Modal patterns without navigation

File Conventions

app/
  layout.tsx          # Root layout (required)
  page.tsx            # Route UI
  loading.tsx         # Loading UI (Suspense boundary)
  error.tsx           # Error boundary
  not-found.tsx       # 404 UI
  route.ts            # API route handler