In a typical modern web application architecture, we have two parts:
the backend server, which serves HTML pages to visitors
With Plone 6, both Classic and Volto Frontend, Webpack is used as tool to gather all the required JS application code and bundle them into static JS files which are loaded by the browsers.
So, included with webpack is the following functionality (all via plugins):
compiling LESS files to CSS, using the
bundling the multiple CSS files together
bundling the multiple JS files
loading other resources, such as images
There is a tendency in the industry to dismiss Webpack and Babel as being complicated and slow. For now it is the solution that provides the optimum amount of features and flexibility, while benefiting from the fact that it's the mainstream solution for these tasks.