[dahauns]

Well duh.

So it's "You just need to go through the webpack Concepts section"...except if you want to actually do some work with it.

See, that's the thing:

If like OP you are an experienced developer freshly coming to web frontend development, the Concepts pages of the webpack docs will tell you very little that you'd find unfamiliar. It's stuff that you've seen a variation of in countless other build systems. (At least that's how it was with me all those years ago.)

But as the docs themselves say: "Plugins are the backbone of webpack". And that's where Pandora's box opens...and where the designation as "just a JavaScript bundler" becomes ridiculous.