**Node.js** is a javascript environment

**Express** is a framework

[What is a software framework?](https://stackoverflow.com/questions/2964140/what-is-a-framework-what-does-it-do-why-do-we-need-a-framework) for Node.js?

Why and when is it useful to use Express framework over Node.js standalone? 

What I mean is that, is this framework just a set of ready functions and modules that makes it easier to write codes from scratch?

I'm asking this because I found lots of tutorials and guides on NodeJS with Express, but just a few on standalone NodeJs.