Module 1 Beginner AZ-900 10 min read

What is Cloud Computing?

Understand the foundation of modern IT — what the cloud is, how it works, the three service models, and why it changed everything about how we build technology.

What you'll learn: Definition of cloud computing · Key characteristics · IaaS vs PaaS vs SaaS · Deployment models · Real-world examples · AZ-900 exam tips

In this tutorial

What is cloud computing?

5 key characteristics

The 3 service models — IaaS, PaaS, SaaS

Deployment models

Why cloud computing matters

AZ-900 exam tips

What is cloud computing?

Cloud computing is the delivery of computing services — including servers, storage, databases, networking, software, and analytics — over the internet. Instead of buying and maintaining physical hardware in your own building, you rent access to these resources from a cloud provider like Microsoft Azure, Amazon Web Services (AWS), or Google Cloud.

Think of it like electricity. You don't build your own power plant at home — you simply plug into the grid and pay for what you use. Cloud computing works the same way for IT infrastructure.

5 key characteristics of cloud computing

1

On-demand self-service — You can provision resources like virtual machines or storage instantly, without needing to contact anyone. You do it yourself through a web portal or API.

2

Broad network access — Resources are available over the internet and can be accessed from any device — laptop, phone, or tablet — from anywhere in the world.

3

Resource pooling — The cloud provider serves multiple customers using the same physical infrastructure, dynamically assigning resources based on demand.

4

Rapid elasticity — Resources can be scaled up or down quickly. If your website gets 10x more traffic overnight, you can scale instantly to handle it — then scale back down to save cost.

5

Measured service — You only pay for what you use. Cloud usage is monitored and billed like a utility — no wasted spend on idle hardware.

The 3 service models

Cloud computing is offered in three main service models. Understanding these is essential for the AZ-900 exam.

1

IaaS — Infrastructure as a Service
You rent the raw infrastructure — virtual machines, storage, networking. You manage the operating system and everything above it. Best for: IT administrators, custom environments.
Azure example: Azure Virtual Machines

2

PaaS — Platform as a Service
You focus only on your application code. The cloud manages the infrastructure, OS, and runtime underneath. Best for: developers who want to build without managing servers.
Azure example: Azure App Service, Azure Functions

3

SaaS — Software as a Service
You use a fully managed application delivered over the internet. Nothing to install or manage. Best for: end users.
Azure example: Microsoft 365, Microsoft Teams

Easy way to remember IaaS vs PaaS vs SaaS: Think of pizza. IaaS = you make your own pizza at home (you manage everything). PaaS = you order a pizza kit (they give you the base, you add toppings). SaaS = you order a delivered pizza (fully ready, nothing to do).

Deployment models

1

Public Cloud — Resources are owned and operated by a cloud provider (like Azure) and shared across many customers. Most cost-effective. Example: hosting your website on Azure.

2

Private Cloud — Resources are used exclusively by one organisation. Can be on-premises or hosted by a third party. More control, higher cost.

3

Hybrid Cloud — A combination of public and private cloud. Organisations keep sensitive data on-premises while using the public cloud for other workloads. Most common in enterprises.

Azure CLI example

bash

        # Create a resource group — your first step in Azure

        az group create \

          --name MyFirstResourceGroup \

          --location centralindia

        # Output confirms your group is created

        { "name": "MyFirstResourceGroup", "location": "centralindia" }

AZ-900 exam tips

✅ Know the 5 characteristics of cloud computing by heart
✅ Be able to identify IaaS, PaaS, SaaS from a scenario description
✅ Understand the difference between public, private and hybrid cloud
✅ Remember: cloud = pay-as-you-go, elastic, self-service