Cloud computing is the delivery of computing resources—including servers, storage, databases,
networking, software, and analytics—over the Internet (“the cloud”) on a pay-as-you-go basis. Instead
of owning and maintaining physical servers or data centers, users can access scalable and
on-demand resources provided by cloud service providers.
Key features of cloud computing include:
1. On-demand self-service: Users can provision resources as needed without human
intervention.
2. Scalability and elasticity: Resources can scale up or down automatically based on demand.
3. Pay-as-you-go pricing: Users pay only for what they use.
4. Broad network access: Services are accessible from anywhere over the internet.
5. Resource pooling: Multiple users share the same physical resources while maintaining
isolation.

Cloud computing is generally classified into three main types based on deployment and service
models:
1. Deployment Models
These describe where the cloud infrastructure is located and who manages it:
a. Public Cloud
● Owned and operated by third-party cloud providers (e.g., AWS, Azure, GCP).
● Resources like servers and storage are shared among multiple organizations.
● Pros: Cost-effective, scalable, no maintenance required.
● Cons: Less control over security and customization.
b. Private Cloud
● Infrastructure is dedicated to a single organization, either on-premises or hosted by a
provider.
● Pros: Enhanced security, full control, compliance-friendly.
● Cons: More expensive, requires IT expertise.
c. Hybrid Cloud
● Combines public and private clouds, allowing data and applications to move between
them.
● Pros: Flexibility, scalability, and better cost optimization.
● Use Case: Sensitive data in private cloud, high traffic workloads in public cloud.

2. Service Models
These describe what type of services the cloud provides:
a. Infrastructure as a Service (IaaS)
● Provides virtualized computing resources over the internet (e.g., EC2, VPC).
● Users manage OS, applications, and storage; providers manage hardware.
b. Platform as a Service (PaaS)
● Provides a platform to develop, run, and manage applications without managing
infrastructure (e.g., AWS Elastic Beanstalk).
c. Software as a Service (SaaS)
● Delivers software applications over the internet on a subscription basis (e.g., Gmail,
Salesforce).
d. Function as a Service (FaaS) / Serverless (optional/advanced)
● Runs code in response to events without managing servers (e.g., AWS Lambda).

An AWS Region is a geographically distinct location where Amazon Web Services (AWS) hosts
its data centers. Each Region consists of multiple Availability Zones (AZs), which are isolated
locations within the region that provide redundancy and high availability.
Key points about AWS Regions:
1. Geographic separation: Each Region is located in a different part of the world to reduce
latency and meet local regulatory requirements.
2. Multiple Availability Zones: Regions have at least two or more AZs to ensure fault tolerance
and disaster recovery.
3. Independent operation: Regions operate independently, so a failure in one region does not
affect others.
4. Service availability: Not all AWS services are available in every Region; some services may
be limited to specific Regions.
Example:
● US East (N. Virginia) – us-east-1
● Europe (Frankfurt) – eu-central-1

An Availability Zone (AZ) is a distinct, isolated data center or a cluster of data centers within an
AWS Region. AZs are designed to provide high availability, fault tolerance, and low-latency
network connectivity between each other.
Key Points about AZs:
1. Isolation: Each AZ is physically separated from others in the same Region to prevent failures
from spreading.
2. Redundancy: AZs have independent power, networking, and cooling systems.
3. Low-latency interconnect: AZs in a Region are connected via high-speed, private fiber-optic
links for fast communication.
4. Disaster recovery: Applications can be deployed across multiple AZs to ensure resilience
against outages.
Example:
● In the US East (N. Virginia) us-east-1 Region, there are 6 AZs (us-east-1a to
us-east-1f).