INTRODUCTION
TO WEB
WHAT IS WEB DEVELOPMENT
Web development is the process of creating and maintaining websites and
web applications that are accessible on the internet. It involves a range of
tasks, from designing the visual layout to writing the code that makes the
site function. Basically, it's how websites are built and kept running
smoothly.
TYPES OF WEB DEVELOPMENT
• Frontend Development (Client-Side)
• Backend Development (Server-Side)
• Full-Stack Development
FRONTEND DEVELOPMENT (CLIENT-SIDE)
What it is: Everything the user sees and interacts with in the browser.
Technologies:
• HTML (structure)
• CSS (design, layout, responsiveness)
• JavaScript (interactivity, dynamic content)
• Frameworks/Libraries: React, Angular,Vue, Svelte
Responsibilities:
• Designing responsive UIs
• Improving performance and accessibility
• Handling user interactions (buttons, forms, animations)
BACKEND DEVELOPMENT (SERVER-SIDE)
What it is: The logic, database, and server-side part of a web app that users don’t see.
Technologies:
• Languages: Node.js, Python, Java, PHP, C#, Go, Ruby
• Frameworks: Express.js, Django, Flask, Spring Boot, Laravel, ASP.NET
• Databases: MySQL, PostgreSQL, MongoDB, Redis
Responsibilities:
• Processing client requests
• Managing databases and APIs
• Implementing authentication & authorization
• Ensuring security and scalability
FULL-STACK DEVELOPMENT
What it is: A combination of frontend + backend. Full-stack developers can build the complete web
application.
Technologies:
• Frontend + Backend tech stacks (MERN, MEAN, PERN, LAMP, etc.)
Responsibilities:
• Building user interfaces
• Handling server logic and databases
• Deploying and maintaining applications
WEB PAGES
A web page is a single document that is displayed through a web browser. It is a part of
a website and can include text, images, videos, links, and interactive elements. Web pages
are primarily written in HTML (HyperText Markup Language), styled with CSS
(Cascading Style Sheets), and have dynamic elements with JavaScript.
A web page shows text, images, and videos to provide information.
It includes elements like forms and buttons that users can click or fill out.
A web page has links that let users move between different pages or sections.
WEB SITES
• A website is a collection of interconnected documents, called web pages, that are
stored on a web server and made accessible to people over the internet using a web
browser. Web pages are connected with each other through hyperlinks.
• The first page of a website is usually the homepage, which acts like the main entrance
or starting point, guiding visitors to other sections of the site.
• Websites can serve many purposes, such as providing information, facilitating
communication, offering online shopping, delivering entertainment, supporting
education, or enabling social networking.
For example: Wikipedia, BBC News .
WEB APPLICATIONS
• A Web Application (Web App) is a software program or application that runs on a web
server and is accessed by users through a web browser over the internet. Unlike
traditional desktop applications that must be installed on each individual device, a web
application runs within a web browser and can be used on multiple platforms and
devices without installation.
• Web applications are interactive and dynamic in nature, meaning they allow
collaborating in real time. They combine the structure and presentation of websites
with the functionality of software applications.
Examples : Amazon, Email ,Youtube.
Feature Website Web Application
Purpose Provides information Allows user interaction and functionality
Interactivity Mostly static (read-only) Dynamic and interactive
User Involvement Users only view content Users can input data and perform actions
Offers features like forms, authentication,
Functionality Displays text, images, videos, and links
and data processing
Online banking, social media, e-commerce
Examples Blogs, news sites, company websites
platforms
Simpler, mainly uses HTML, CSS, and basic More complex, involving backend logic,
Development Complexity
JavaScript databases, and APIs
Requires regular updates for new features
Updates Content updates occasionally
and improvements
Often requires login and user
Authentication Usually not required
authentication
NETWORK
• A network is a system of interconnected devices that communicate and share resources
with each other either physically or wirelessly.
INTERNET
Internet = Interconnected Networks
Inter → means connections between many different networks.
Net → short form of network. A group of interconnected computers or devices that share information.
The Internet is a global system of interconnected computer networks that connects billions of
devices worldwide. It enables communication, data exchange, and information sharing across the
globe.
It facilitates various online services like email, websites, social media, and more.The Internet's core is a
system of interconnected networks that allow data to travel across vast distances.
CLIENT-SERVER ARCHITECTURE
CLIENT-SERVER ARCHITECTURE
• Computers connected to the internet are called clients and servers.
• Clients and servers exchange messages in a request–response messaging pattern. The client sends a
request, and the server returns a response to received request.
• Clients are the typical web user's internet-connected devices (for example, your computer connected
to your Wi-Fi, or your phone connected to your mobile network) and web-accessing software available
on those devices (usually a web browser like Firefox or Chrome).
• Servers are computers that store webpages, sites, or apps. When a client wants to access a webpage, a
copy of the webpage code is downloaded from the server onto the client machine to be rendered by
the browser and displayed to the user.
HOW THE WEB WORKS
HOW THE WEB WORKS
• The browser goes to the DNS server and finds the real address of the server that the
website lives on.
• The browser sends an HTTP request message to the server, asking it to send a copy of the
website to the client .This message, and all other data sent between the client and the server,
is sent across your internet connection using TCP/IP.
• If the server approves the client's request, the server sends the client a "200 OK" message,
and then starts sending the website's files to the browser as a series of small chunks
called data packets.
• The browser assembles the small chunks into a complete web page and displays it to you.
History of Internet
EARLY DEVELOPMENT (1960S – 1970S)
1960s:
• The idea of connecting computers together began.
• The U.S. Department of Defense created ARPANET (Advanced Research Projects
Agency Network) in 1969.
• ARPANET was the first computer network that allowed researchers to share information.
1970s:
• Development of TCP/IP protocol (Transmission Control Protocol / Internet Protocol).
• This became the foundation of the Internet, standardizing how computers communicate.
THE BIRTH OF THE INTERNET (1980S)
• ARPANET expanded and connected universities, research labs, and government
organizations.
• In 1983, ARPANET officially switched to TCP/IP, marking the official start of the
Internet.
• Domain Name System (DNS) introduced in 1984 → allowed easy names like
www.example.com instead of long numbers (IP addresses).
THE WORLD WIDE WEB (1990S)
1989–1990: Tim Berners-Lee (a scientist at CERN) invented the World Wide
Web (WWW).
• Introduced HTML, URLs, and HTTP.
• First website went live in 1991.
1993: Mosaic, the first popular web browser, launched.
Mid-1990s:
• Growth of websites, email, online chat.
• Companies like Yahoo (1994), Amazon (1995), Google (1998) emerged.
WEB 1.0 (1990S – EARLY 2000S)
• Known as the “Static Web.”
• Websites were simple, read-only pages.
• Users could only read information, not interact much.
• Examples: early news sites, personal homepages.
WEB 2.0 (2000S – 2010S)
• Known as the “Social Web.”
• Websites became interactive and dynamic.
• Users could create and share content → rise of blogs, social media,
YouTube, Facebook,Twitter.
• Growth of e-commerce (Amazon, eBay) and web applications
(Google Docs, Gmail).
HTTP
• HTTP (Hypertext Transfer Protocol) is a fundamental protocol of the
Internet, enabling the transfer of data between a client and a server. It is the
foundation of data communication for the World Wide Web.
• HTTP provides a standard between a web browser and a web server to establish
communication. It is a set of rules for transferring data from one computer to
another. Data such as text, images, and other multimedia files are shared on the
World Wide Web. Whenever a web user opens their web browser, the user
indirectly uses HTTP.
HTTP REQUEST/RESPONSE:
• HTTP is a request-response protocol, which means that for every request
sent by a client (typically a web browser), the server responds with a
corresponding response. The basic flow of an HTTP request-response
cycle is as follows:
• Client sends an HTTP request: The client (usually a web browser)
initiates the process by sending an HTTP request to the server. This
request includes a request method (GET, POST, PUT, DELETE, etc.), the
target URI (Uniform Resource Identifier, e.g., a URL), headers, and an
optional request body.
• Server processes the request: The server receives the request and
processes it based on the requested method and resource. This may involve
retrieving data from a database, executing server-side scripts, or performing
other operations.
• Server sends an HTTP response: After processing the request, the
server sends an HTTP response back to the client. The response includes a
status code (e.g., 200 OK, 404 Not Found), response headers, and an optional
response body containing the requested data or content.
• Client processes the response: The client receives the server's response
and processes it accordingly. For example, if the response contains an HTML
page, the browser will render and display it. If it's an image or other media file,
the browser will display or handle it appropriately.
METHODS OF HTTP
• GET: Used to retrieve data from a specified resource. It should have no side
effects and is commonly used for fetching web pages, images, etc.
• POST: Used to submit data to be processed by a specified resource. It is
suitable for form submissions, file uploads, and creating new resources.
• PUT: Used to update or create a resource on the server. It replaces the
entire resource with the data provided in the request body.
• PATCH: Similar to PUT but used for partial modifications to a resource. It
updates specific fields of a resource rather than replacing the entire resource.
• DELETE: Used to remove a specified resource from the server.
Status Codes
Status Code Description
1xx: It means the request has been received and the process is
Informational continuing.
It means the action was successfully received, understood,
2xx: Success
and accepted.
It means further action must be taken in order to
3xx: Redirection
complete the request.
It means the request contains incorrect syntax or cannot
4xx: Client Error
be fulfilled.
It means the server failed to fulfill an apparently valid
5xx: Server Error
request.
• 200 OK → Request succeeded, and the server returned the expected data
• 301 Moved Permanently → Resource has been permanently moved to a
new URL.
• 400 Bad Request → Client sent an invalid request (e.g., malformed syntax).
• 404 Not Found → Requested resource could not be found on the server.
• 500 Internal Server Error → Generic server error when something goes
wrong.
IP ADDRESS
• An IP address is a unique numerical label assigned to each device on a
network.
• It identifies both the device and its location on the internet.
• It allows devices to communicate with each other over the internet.
• Every website and computer connected to the internet has an IP address.
• Example: 192.168.1.1.
DOMAIN NAME
• A domain name is the human-friendly address of a website.
• It is used instead of numerical IP addresses.
• Example: typing google.com instead of 142.250.192.46.
• Domain names are unique for each website on the internet.
• They make it easier to find and access websites.
DNS (DOMAIN NAME SYSTEM)
• DNS is a hierarchical and distributed naming system that translates
domain names into IP addresses. When you type a domain name
your browser, DNS ensures that the request reaches the correct
server by resolving the domain to its corresponding IP address.
• Without DNS, we’d have to remember the numerical IP address of
every website we want to visit, which is highly impractical.
Working of
DNS
• User Input: You enter a website address (for example, www.geeksforgeeks.org) into
your web browser.
• Local Cache Check: Your browser first checks its local cache to see if it has
recently looked up the domain. If it finds the corresponding IP address, it uses that
directly without querying external servers.
• DNS Resolver Query: If the IP address isn’t in the local cache, your computer
sends a request to a DNS resolver. The resolver is typically provided by your Internet
Service Provider (ISP) or your network settings.
• Root DNS Server: The resolver sends the request to a root DNS server . The root
server doesn’t know the exact IP address for www.geeksforgeeks.org but knows which
Top-Level Domain (TLD) server to query based on the domain’s extension (e.g., .org).
• TLD Server: The TLD server for .org directs the resolver to the authoritative DNS
server for geeksforgeeks.org.
• Authoritative DNS Server: This server holds the actual DNS records for
geeksforgeeks.org, including the IP address of the website’s server. It sends this IP
address back to the resolver.
• Final Response: The DNS resolver sends the IP address to your computer, allowing it
to connect to the website’s server and load the page.
HOSTING
• Hosting is a service that provides storage space, server
resources, and network connectivity so that your
website/application can be accessible on the Internet 24/7.
HOW HOSTING WORKS
• You build a website on your local computer.
• You purchase a domain name (example: www.example.com)
• You rent hosting space from a provider (like AWS, Google Cloud).
• You upload your website/app files to the hosting server.
• When users type your domain, the DNS system points them to your hosting server’s IP
address.
• The hosting server delivers the files/webpage to the user’s browser.
