Node.js or Node js is an open-source and cross-platform JavaScript runtime environment. It is open-source that means everyone has rights to use it, study it, change it, and even distribute its source code to anyone and for any purpose.
Node.js is cross platform so it can runs on various platforms like Windows, Linux, Unix, Mac OS X, etc. Since Node.js runs on V8 JavaScript engine, the core of Google Chrome, it is very performant.