A modern JavaScript web application includes a lot of different packages and dependencies, and it's important to have something that makes sense of it all in a simple way.
Angular 2 takes the approach of breaking your application apart into many different components, each of which can have several files. Separating application logic this way is good for the programmer, but can detract from user experience since doing this can increase page loading time. HTTP2 aims to solve this problem in one way, but until more is known about its effects we will want to bundle different parts of our application together and compress it.
Our platform, the browser, must continue to provide backwards compatibility for all existing code and this necessitates slow movement of additions to the base functionality of HTML/CSS/JS. The community has created different tools that transform their preferred syntax/feature set to what the browser supports to avoid binding themselves to the constraints of the web platform. This is especially evident in Angular 2 applications, where TypeScript is used heavily. Although we don't do this in our course, projects may also involve different CSS preprocessors (sass, stylus) or templating engines (jade, Mustache, EJS) that must be integrated.
Webpack solves these problems by providing a common interface to integrate all of these tools and that allows us to streamline our workflow and avoid complexity.