Chapter 02 — What is Cloud Computing?

What is Cloud Computing?

Cloud computing is the delivery of computing services — including servers, storage, databases, networking, software, analytics, and intelligence — over the internet ("the cloud") to offer faster innovation, flexible resources, and economies of scale.

Instead of owning and maintaining physical hardware and data centers, you rent access to computing resources from a cloud provider and pay only for what you use.

Simple analogy: Think of cloud computing like electricity. You don't build your own power plant — you plug into the grid and pay for what you consume. Cloud computing works the same way for IT resources.

Traditional IT vs. Cloud Computing

Before cloud, every company had to build and manage its own IT infrastructure:

How Cloud Computing Works

Here is a simplified view of what happens when you use cloud services:

Your Device (Laptop / Phone / Browser)
        │
        │  Internet
        ▼
  Cloud Provider Data Center
  ┌─────────────────────────────┐
  │  Servers   Storage   Network │
  │  Databases  AI/ML   Security │
  └─────────────────────────────┘
        │
        │  You access resources on-demand
        │  You pay only for what you use

The cloud provider owns and operates massive data centers around the world. You access those resources remotely through the internet — no physical hardware on your end required.

The 5 Essential Characteristics of Cloud Computing

The National Institute of Standards and Technology (NIST) defines cloud computing by 5 characteristics. These are widely accepted globally and relevant to the AZ-900 exam.

1. On-Demand Self-Service

You can provision computing resources (like spinning up a virtual machine or creating a storage bucket) automatically, without human interaction from the service provider.

You go to the Azure portal, click a few buttons, and a server is running in minutes — no call to a sales rep needed.

2. Broad Network Access

Resources are available over the internet and can be accessed from any device — laptop, smartphone, tablet — from anywhere in the world.

Your Azure-hosted app is accessible from Tokyo, New York, and Lagos simultaneously.

3. Resource Pooling

The cloud provider pools computing resources to serve multiple customers using a multi-tenant model. Resources (storage, processing, memory) are dynamically assigned and reassigned according to demand.

You share the underlying physical infrastructure with other customers — but your data and workloads remain isolated and secure.

4. Rapid Elasticity

Resources can be quickly scaled up or down to match demand. From the user's perspective, the resources often appear unlimited.

An e-commerce site can automatically scale from 10 servers to 1,000 servers during a flash sale — then scale back down when traffic drops.

5. Measured Service

Cloud systems automatically control and optimize resource usage. Usage is monitored, controlled, and reported transparently — you pay for exactly what you consume.

Like a water meter — you only pay for the litres of water you actually used.

Key Cloud Terminology for Beginners

Why Organizations Move to the Cloud

Top Reasons for Cloud Adoption:
────────────────────────────────
  ✓ Reduce IT costs
  ✓ Scale faster
  ✓ Go global quickly
  ✓ Improve security and compliance
  ✓ Enable remote work
  ✓ Innovate faster (AI, ML, analytics)
  ✓ Reduce time to market

Microsoft Azure and Cloud Computing

Microsoft Azure is one of the world's leading cloud platforms. It offers 200+ services across compute, storage, networking, AI, security, and more — all delivered through the cloud model described in this chapter.

Azure follows all 5 NIST characteristics and allows you to:

• Spin up servers in seconds

• Store unlimited data

• Deploy apps globally

• Pay only for what you use

Quick Recap

Cloud Computing in a Nutshell:
──────────────────────────────
  Rent IT resources over the internet
  Pay as you go (no upfront hardware)
  Scale up or down instantly
  Access from anywhere, any device
  Provider manages the infrastructure

Official References

• What is cloud computing? — Microsoft Learn

• Introduction to Azure — Microsoft Learn

• AZ-900 Learning Path — Microsoft Learn

Next Chapter → Chapter 03: Benefits of Cloud Computing