Node.js is designed to efficiently handle many tasks at the same time, such as serving web requests, reading files, or interacting with databases. The core mechanism that enables this efficiency is called the event loop. The event loop is a fundamental part of Node.js that allows it to perform non-blocking operations—meaning Node.js can start a task, move on to the next one, and return to finish the first task when it is ready, all without stopping the main thread.

When you execute code in Node.js, the event loop is always running in the background. It constantly checks for new tasks, operations that have finished, and events that need to be handled. If you make a request to read a file, for example, Node.js will hand off that task to the system and keep running other code. When the file is ready, the event loop notices and lets your code know so you can handle the file’s contents.

This design is different from traditional blocking code, where each operation must finish before the next one starts. Instead, the event loop lets Node.js manage thousands of operations at once, making it ideal for servers and applications that need to handle many users or tasks at the same time.