Officially, Node.js is defined thus:
Important to note here is Node.js is a
Node is written in C++ programming language.
Node.js is useful in a number of real-world applications. For building JSON APIs, Single page Applications, Data Streaming Applications, I/O applications (it can also interact with the file systems and Operating system) etc.
Node.js is Asynchronous, Event driven, fast and is single-threaded with event-looping.