To understand why we use webpack, let's recap how we used JavaScript on the web before bundlers were a thing.

There are two ways to run JavaScript in a browser. First, include a script for each functionality; this solution is hard to scale because loading too many scripts can cause a network bottleneck. The second option is to use a big .js file containing all your project code, but this leads to problems in scope, size, readability and maintainability.

In the context of using multiple scripts in a web application without a bundler like webpack, the following factors contribute to a potential network bottleneck:

1. Network requests: Each script file included in the HTML document requires a separate network request. When there are many scripts, each request adds additional overhead in terms of establishing a connection, sending the request, and receiving the response. This can increase the overall load time of the web page.
2. Connection limits: Web browsers have a limit on the number of concurrent connections they can make to a single domain. Older browsers typically had a limit of around 4-6 connections per domain, while modern browsers allow more concurrent connections. However, even with higher limits, a large number of scripts can saturate the available connections, leading to delays in loading other resources.
3. Network latency: Each network request incurs a certain amount of latency, which is the time it takes for a round trip between the client and the server. This latency includes the time taken to establish the connection, send the request, and receive the response. When there are multiple script files, the cumulative latency can significantly impact the overall load time, especially when the client and server are geographically distant.
4. File size overhead: Each script file has its own file size, including any associated whitespace, comments, and redundant code. This redundancy increases the total amount of data that needs to be transferred over the network. When there are many script files, the combined size can be substantial, leading to increased bandwidth usage and slower loading times.

By utilizing webpack's capabilities, we can optimize the performance of our website/application, improve code maintainability, and streamline our development workflow. It simplifies the process of bundling and managing complex JavaScript projects, making it an essential tool in modern web development. Here are some key reasons why we need webpack:

1. Module Bundling: webpack allows us to organize our JavaScript codebase into modular pieces called modules. It can intelligently analyze your code, identify dependencies between modules, and bundle them into a single file or multiple files (depending on the configuration). This bundling process improves performance by reducing the number of requests made by the browser to fetch individual files, resulting in faster page load times.
2. Dependency Management: With webpack, we can easily manage dependencies between different modules or libraries used in our project. It can resolve and handle complex dependency trees, ensuring that all the required modules are included in the bundle and that they are loaded in the correct order. This eliminates manual management of script tags or worrying about the order of script inclusion in HTML files.
3. Code Splitting: webpack enables code splitting, which is the process of breaking your application code into smaller chunks based on dynamic points of separation. Code splitting allows us to load only the necessary parts of our application when needed, improving initial page load times and reducing the overall size of the bundle. It also helps implement features like lazy loading, where certain sections of your application are loaded on-demand to improve performance.
4. Asset Management: In addition to JavaScript modules, webpack can handle various other types of assets, such as stylesheets, images, fonts, and more. By using loaders, you can process these assets and incorporate them into your bundle. webpack can optimize and transform these assets, such as compressing images or converting stylesheets to a compatible format, improving performance and reducing the overall file size.
5. Development Workflow: webpack provides a robust development workflow by offering features like live reloading, hot module replacement, and a development server. These features enable a seamless development experience where changes made in our code are automatically reflected in the browser without requiring a manual page refresh. This significantly speeds up the development process and enhances productivity.
6. Extensibility and Customization: webpack is highly extensible and customizable. It provides a rich ecosystem of plugins and loaders that allow us to enhance and tailor the bundling process to fit our project's specific needs. We can leverage community-contributed plugins or create our own to add functionality, such as code linting, static analysis, or optimization techniques.