What is node.js

Answer 1

It's simply a platform that allows us implement JavaScript on the backend, and that's just scratching the surface.
Check out http://whatis.techtarget.com/definition/Nodejs

Answer 2

it's a console like a Linux console where you can install some application who are used like plugin but for that you have to install npm on it... this is what I know of node.js. Personally I use it for firebase. Go see the web site of npm by searching on Google npm and node.js. On this site they have some documentation