# Back End with Nodejs

### What is a Website and Web Application?

**Website:-**

A set of pages of information on the internet about a particular subject, published by a single person or organization.

**Examples:-** Wikipedia, News, Blogs

**Web Application:-**

A ***web application*** is a computer program that utilizes web browsers and web technology to perform tasks over the Internet.

**Examples:-** Instagram, Facebook, and youtube.

**To build Web Applications we follow 3 tier architecture**

* Frontend
    
* Backend
    
* Database
    

### Three Layered Architecture to build the Backend

1. Router
    
2. Controller
    
3. Model
    

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1706978466142/8ac8f832-6d71-45d6-8085-0881c32d9c4d.png align="center")

### Router:-

***Routing*** in ***Node*** refers to the process of determining how an application responds to client requests to different endpoints (URLs).

### Controller:-

Controllers are **responsible for handling incoming requests and returning responses to the client**. A controller's purpose is to receive specific requests for the application. The routing mechanism controls which controller receives which requests.

### Database:-

It refers to the information stored in a database, such as customer details, product inventory, or financial records. They provide a structured way to store and retrieve data, ensuring data integrity and security.