What is Node.js?
Node.js is a server side scripting language which helps to build the scalable application. It uses Javascript to write code.
Why Javascript?
Earlier days, javascript used to work only in the web browsers i.e we used for the client side validations, making Ajax requests and etc... But original developers of Javascript extended it from something you could do beyond the browser.
How does that work?
Lets compare the nodejs with Java.
Node.js runs on top of google v8 engine. Why Node is fast? because of v8 engine which written in C++ and provides better performance because of optimization, inline caching and etc...
Google V8 Engine
The V8 Engine which is built by Google is open source and written in C++. This engine is used inside Google Chrome. It was designed to increase the performance of Javascript execution inside the web browsers. In order to get the speed, V8 translates Javascript code into more efficient machine code instead of using an interpreter.
Why Google developed V8 Engine?
When google introduced a new application Google Maps in 2004.It is a game changer for javascript and developers. But it got a performance bottleneck.It was a very very slow. To overcome this issue, Google built its own engine which powers Chrome and Node.js. Before V8, javascript was more of a interpreted language but google changed the language from interpreted to JIT compiled language.