How to build bundles with webpack?

Question

JavaScript

Good afternoon. I'm trying to understand webpack for use in normal sites and I can't figure out how it works. Before that, I compiled everything on gulp. Actually the questions themselves:
1. How can I collect 10/100/1000 js files into a single bundle.js without manual import / require in some main.js ?
2. How to collect separately 10/100/1000 css files into one bundle.css without manual Dmitrijs Balcers ?
How the hell does it even work?