Summary
This chapter explains the separation of concerns between client-side (frontend) and server-side (backend) code, detailing their distinct responsibilities and the data flow between them.

General domain of usage
Web application development


Web applications are usually divided into two parts: **frontend** and **backend**.

The **frontend** is everything you see and interact with in your browser.

For example:

* Buttons;
* Forms;
* Text and images.

This is the visual part of an application.



The **backend** is everything that happens behind the scenes.

It is responsible for:

* Processing data;
* Handling logic;
* Storing and retrieving information.

Users don't see the backend, but it powers the application.







Imagine a login form.

* You enter your email and password;
* The frontend sends this data to the backend;
* The backend checks if the data is correct;
* The result is sent back to the frontend;
* You are logged in (or see an error).




## How They Work Together

Frontend and backend are always connected:

1. Frontend → sends data;
2. Backend → processes it;
3. Backend → sends result;
4. Frontend → shows it.



Understand how the web works and how frontend, backend, and databases connect to form a complete application. Explore the role of fullstack development and the technologies used across the track, including HTML, CSS, JavaScript, React, Node.js, Express.js, and MongoDB. Build a clear mental model of how data flows through an application before starting hands-on development.

Frontend vs Backend

How They Work Together