Built-in modules are the building blocks of any Node.js application, providing core functionality out of the box.
1File System (fs)
The fs module is one of the most used. It provides both synchronous and asynchronous methods. In a high-concurrency server, always prefer the asynchronous versions like fs.readFile to keep the Event Loop free.
2HTTP Networking
With http.createServer(), you can spin up a web server in just a few lines of code. It gives you full control over the request and response objects, which is the foundation for frameworks like Express.
3Path & OS Utilities
Building cross-platform apps requires careful path handling. path.join() and path.resolve() ensure your code works on Windows, Linux, and macOS without manual string manipulation.
4EventEmitter
Node.js is event-driven. Many core modules (like http and fs streams) inherit from EventEmitter. You can also create your own custom events to decouple your application logic.
