One of the first confusion, which anyone beginning with node.js faces, is that whether its a new language, or is it a framework or is it a library?
Well, actually its none of these.
Node.js is niether a language nor its a framework and also its not a library. Rather, its a run time environment.
Thus, if asked – What is node.js? – one can confidently and clearly reply – Its a Runtime Environment.
Hope this helps.