Handling API calls and storing sensitive information, such as API keys or other credentials, on the back-end (server-side) is an important practice in web development. This approach offers some key benefits:

• Security: Placing sensitive information on the server-side reduces the risk of exposing that information to the public, including potential malicious users. If sensitive data like API keys were stored on the front-end (client-side), they could be easily accessed by anyone with access to the client code, which could lead to unauthorized access to the API or other security issues.

• Simplification: Placing API calls on the server-side allows for a cleaner and more simplified separation of concerns. The client-side code can focus on user interactions and presentation, while the server-side handles data processing and interactions with external services like APIs. This allows the client-side to focus on its primary responsibility, which is providing a smooth user experience. Meanwhile, the server-side handles the more technical aspects.

In a client-server setup, the server acts like a messenger between the front-end and the back-end. Below is an illustration explaining this process:

When a user interacts with the browser (e.g., by clicking a button or submitting a form), the browser sends a request to the server to perform certain actions or retrieve data. The server then processes the request, which may include interacting with databases and communicating with other external services (like APIs). Once the server has completed its processing, it sends back a response to the browser. The response can contain the results of a request, data, or any error messages, which the browser uses to update the user interface and provide feedback to the user.