What is Cloud Computing?

The Simple Definition

Cloud computing means using someone else's computers over the internet instead of owning and managing your own hardware.

Before the cloud, if you wanted to run a website you had to:

Buy physical servers
Rent space in a data center
Set up networking, power, cooling
Hire people to maintain it
Overprovision for peak traffic (waste money most of the time)

With the cloud, you rent computing resources on demand and pay only for what you use.

Why Cloud Computing Exists

Amazon built massive data center infrastructure for their own e-commerce business. In 2006 they realized they could rent out the spare capacity. AWS was born — and it changed everything.

The Five Characteristics of Cloud Computing

The Three Service Models

IaaS — Infrastructure as a Service

You get raw compute, storage, and networking. You manage everything above the hardware.

You manage: OS, runtime, middleware, apps, data
Provider manages: servers, storage, networking, virtualization
Examples: AWS EC2, Google Compute Engine, Azure VMs

PaaS — Platform as a Service

You get a platform to deploy your application. No server management.

You manage: apps, data
Provider manages: everything else including OS and runtime
Examples: Heroku, AWS Elastic Beanstalk, Google App Engine, Vercel

SaaS — Software as a Service

You use the software. You manage nothing.

You manage: your data and settings
Provider manages: everything
Examples: Gmail, Slack, Salesforce, GitHub

The Three Deployment Models

Model	Cost	Control	Use case
Public	Pay per use	Low	Startups, variable workloads
Private	High upfront	Full	Banks, healthcare, compliance
Hybrid	Mixed	Mixed	Enterprise with legacy systems

The Major Cloud Providers

Provider	Market share	Strengths
AWS	~32%	Broadest services, most mature
Azure	~23%	Enterprise, Microsoft integration
GCP	~12%	AI/ML, data analytics, Kubernetes
Others	~33%	Cloudflare, DigitalOcean, Vercel

AWS launched in 2006 and has a 6-year head start. Most companies use AWS as their primary cloud.

Key Benefits

Cost efficiency — No upfront capital expenditure. Pay for what you use. Shut down resources when not needed.

Speed — Provision a server in 60 seconds. Deploy globally in minutes.

Global reach — AWS has data centers in 33 regions worldwide. Serve users with low latency anywhere.

Reliability — Cloud providers offer 99.99%+ uptime SLAs backed by redundant infrastructure.

Security — Major providers invest billions in security. Often more secure than self-managed infrastructure.

Real-World Example

Netflix on AWS:

Streams to 260 million subscribers globally
Uses AWS in multiple regions for redundancy
Auto-scales during peak hours (Friday evenings)
Pays only for what it uses — scales down at 3am
Would cost billions to build equivalent infrastructure themselves

Key Takeaway

Cloud = renting computing resources on demand over the internet
Three models: IaaS (raw infra), PaaS (platform), SaaS (software)
Three deployments: public, private, hybrid
AWS dominates with ~32% market share
Key benefits: cost, speed, scale, global reach, reliability