What is Cloud Computing

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

Why Cloud Computing Matters

Before the cloud, organisations had to buy and maintain their own physical servers, storage devices, and networking equipment. This meant:

High upfront costs — purchasing hardware before you even write a line of code
Capacity guessing — buying too much (wasted money) or too little (unable to scale)
Slow provisioning — weeks or months to procure and set up new servers
Maintenance burden — patching, cooling, power, and physical security all fall on you

Cloud computing removes these constraints. You rent what you need, when you need it, and pay only for what you use.

Key Characteristics of Cloud Computing

The National Institute of Standards and Technology (NIST) defines five essential characteristics:

1. On-Demand Self-Service

You can provision resources (servers, storage, etc.) automatically without needing human intervention from the provider.

2. Broad Network Access

Resources are available over the network and accessed through standard mechanisms — a web browser, CLI, or API.

3. Resource Pooling

The provider's resources are pooled to serve multiple customers using a multi-tenant model. You don't know (or need to know) the exact physical location of your resources.

4. Rapid Elasticity

Resources can be elastically provisioned and released to scale rapidly. To the consumer, the available resources often appear unlimited.

5. Measured Service

Cloud systems automatically control and optimise resource use by leveraging a metering capability. You only pay for what you consume.

Cloud Service Models

There are three primary service models, each offering a different level of abstraction:

Model	What You Manage	What the Provider Manages	Example
IaaS (Infrastructure as a Service)	OS, runtime, app, data	Servers, storage, networking	Amazon EC2, Azure VMs
PaaS (Platform as a Service)	App and data	OS, runtime, servers, storage	AWS Elastic Beanstalk, Heroku
SaaS (Software as a Service)	Nothing — just use it	Everything	Gmail, Salesforce, Slack

IaaS — Most Control

You get virtual machines, storage, and networks. You install and manage the operating system and everything above it.

PaaS — Balanced

You deploy your application code. The provider handles the operating system, runtime, and infrastructure.

SaaS — Least Control

You use a finished application over the internet. The provider manages everything.

Cloud Deployment Models

Public Cloud

Resources are owned and operated by a third-party provider and delivered over the internet. Examples: AWS, Microsoft Azure, Google Cloud Platform (GCP).

Private Cloud

Cloud infrastructure is provisioned for exclusive use by a single organisation. It can be on-premises or hosted by a third party.

Hybrid Cloud

A combination of public and private clouds, bound together by technology that allows data and applications to be shared between them.

Benefits of Cloud Computing

Benefit	Description
Trade capex for opex	No upfront hardware investment; pay as you go
Massive economies of scale	Providers buy at huge scale, passing savings to you
Stop guessing capacity	Scale up or down based on actual demand
Increase speed and agility	Provision resources in minutes, not months
Go global in minutes	Deploy to data centres worldwide with a few clicks
Focus on your product	Spend time on differentiation, not infrastructure

Summary

Cloud computing fundamentally changes how organisations consume IT resources. Instead of owning hardware, you rent it on demand. Understanding the service models (IaaS, PaaS, SaaS) and deployment models (public, private, hybrid) is essential before diving into any specific cloud provider.

In the next lesson, we'll introduce Amazon Web Services (AWS) — the world's most widely adopted cloud platform.