Ask HN: Understand Javascript tools

So currently I'm learning Javascript from a Python background. I like Javascript but lately there is talk about how you can use it for backend and I'm not sure how that works.

Someone explain to me these tools and how they all fit together to build a production site? or even a simple blog perhaps.

Javascript, jQuery, Nodejs, Backbonejs, Expressjs, Underscorejs and bower and NPM, Angularjs, Emberjs.

I'm having hard time understanding how these all fit together and how they help each other or use to build a website both frontend and backend, thanks.