Types

• Private
• Public
• Hybrid

Private: Cloud for one

Natural evolution from the traditional corporate data center. After all, a private data center is still a cloud, delivering IT services over the internet, and can also use the self‑service model where users can provision and set up their own VM for work purposes.

It is only used by a single entity. Only a single organization will be using this private cloud. Because of that, it is often maintained by that organization, and you get much better security and privacy as a result. After all, no one else is using it except your company.

Is similar to a typical on‑premises data center environment

It has a few caveats:

• cost: as companies need to provision their own hardware
• maintenance: they need IT staff to manage and setup services
• less flexible: compared to their public cloud counterparts just due to the sheer number of different managed services that public clouds come with.

Considerable more overhead to manage it.

In summary private clouds:

• Use the Self-service model
• Completely private - no outside access
• Better security and privacy
• Your own hardware = high upfront cost
• More responsibility - in charge of hardware
• Less flexibility compared to public cloud

Public: Cloud for everyone

Built, controlled, and maintained by a third‑party provider (Microsoft, Amazon, Google, DigitalOcean, etc.). Anyone who wants to purchase services can access and use those resources immediately, with no upfront investment, that plus general public availability is the main difference from a private cloud.

Caveats:

• shared tenancy with other customers on the same underlying resources
• no control over which physical server your workloads land on
• not inherently insecure, but organizations with extreme privacy/security requirements should be aware of and compensate for these points

In summary public clouds:

• Cloud for the masses - available to anyone
• No upfront cost
• Vendor owns and maintains the hardware
• More flexibility - wide variety of managed services
• Less control over physical environment
• Shared tenancy

Hybrid: Best of both worlds

Combines a private cloud (or on‑premises) with a public cloud, connected via private connectivity such as VPN or a dedicated line (e.g. Azure ExpressRoute).

• Biggest advantage: flexibility, run each workload where it belongs. Highly sensitive workloads that can't tolerate shared tenancy stay on the private/on‑prem side; everything else can run in the public cloud while still connecting privately back.
• Biggest drawback: complexity, you need the skill set to manage two (or more) different environments/management planes instead of one.

Variations of the hybrid model:

• Multi‑cloud: not limited to public+private; can also mean connecting multiple public clouds to each other (e.g. Azure, AWS, GCP) over private connectivity, typically VPN.
• Azure Arc: an Azure management feature that extends Azure's management plane to workloads outside Azure (on‑prem or other clouds), letting you manage Azure and non‑Azure resources from one place.

Summary: the three models

• Private: cloud for one (single customer): full control and privacy, at the cost of maintenance and high upfront investment.
• Public: cloud for all: no upfront cost and more flexibility, at the cost of less control over the physical environment.
• Hybrid: best of both: connects public with private (or public with public) over private connectivity, maximizing flexibility at the cost of managing more complexity.