NodeJS mirrors how JavaScript runs on the browser using a specific JavaScript engine (Chrome V8 engine). On top of that, it adds some features that makes it run on the server. If you really want to know how NodeJS works, start from understanding how JavaScript runs on the browser. In other words, How the browser uses the JavaScript engine (i.e V8 Engine which NodeJS is built on top of), Event Loop, Event Queue and Job Queue to execute JavaScript codes. This will just give you the high-level overview of how JavaScript works, but it will aid you a lot in understanding how NodeJS works. There are tons of blogs, articles, and videos out there in google that discuss this. You just have to use the right word, i.e "How does javascript work in the browser with event queue and V8 engine" and you would have your answers. Hope this helps!