Teach Webpack how to understand files that JavaScript cannot handle by itself.
Webpack can understand JavaScript and JSON by default, but real applications contain many other file types such as CSS, images, and TypeScript. Loaders transform these files into something Webpack can process and include in your application.
For example, a loader can transform TypeScript into JavaScript or process CSS before it becomes part of your bundle. Loaders are configured with rules that tell Webpack which files they should handle and what transformation should happen.
What you'll walk away knowing