510 How web applications work

Exploring the structure and communication flow that enables web software to operate.

Outline

This chapter introduces the fundamentals of how web applications function on the internet. Students investigate the client-server model, the transmission of data using protocols and packet structures, and the key technologies that support communication between browsers and servers. Understanding these foundational concepts is essential before diving into front-end and back-end development in later chapters.

Targets

In this topic, students learn to:

• Identify the components of a web application and how they interact

• Describe how data is transmitted using protocols such as HTTP and TCP/IP

• Explain the role of domain names, IP addresses and DNS in locating web resources

• Investigate web protocols and their purpose, including standard port numbers

• Recognise the relationship between front-end and back-end systems in delivering a web experience

Glossary

Term	Definition
Web application	A program accessed via a web browser that runs on remote servers.
Client-server model	A computing model where a client sends requests and a server responds.
Data packet	A unit of data transmitted over a network, containing both payload and header.
IP address	A unique numerical identifier assigned to a device on a network.
DNS	Domain Name System; translates domain names into IP addresses.
HTTP/HTTPS	Protocols for transmitting web content; HTTPS adds encryption.
TCP/IP	A suite of protocols used for data communication on the internet.
Ports	Logical access points for communication protocols (e.g. port 80 for HTTP).
Protocol	A set of rules for formatting and transmitting data between systems.

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Overview

Every time we load a webpage, click a link or submit a form, a series of digital events occur behind the scenes. Web applications rely on a complex but structured set of interactions between clients (typically browsers) and servers that handle requests and return responses. These interactions are governed by web protocols such as HTTP, DNS and TCP/IP.

In this chapter, students build a conceptual model of how data moves across the Internet. They will explore how data is packaged, addressed, routed and delivered through the use of data packets, IP addresses and domain names. Key web communication protocols are introduced, and students are encouraged to visualise the request–response cycle using real-world examples such as visiting a website or logging into an online service.