Define cloud computing

az-900•beginner•January 1, 2025

cloudfundamentals

Cloud concepts

Define Cloud Computing

Short Summary

In this lesson, we explain what cloud computing is (and what it is not) using a simple definition you can reuse. We also cover the five essential characteristics that distinguish cloud computing from “just using the internet.” By the end, you should be able to recognize cloud scenarios quickly and avoid the most common misunderstandings.

Learning Objectives

By the end of this lesson, you will be able to:

Define cloud computing in one clear sentence.
List the five essential characteristics of cloud computing.
Distinguish “using the internet” from “using cloud computing” as a delivery model.
Explain why cloud computing is about speed and flexibility, not only cost savings.
Summarize how responsibilities shift across Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).

Core Concepts

Cloud computing is the on-demand delivery of computing services (such as servers, storage, databases, networking, and software) over a network (most often the internet). Instead of buying and maintaining physical infrastructure, you use a cloud provider’s resources when you need them, and you typically pay based on what you consume.

A useful term here is provision: it simply means “create and make ready to use.” If I can create compute or storage via a portal, an Application Programming Interface (API), or automation—and scale it up or down without buying hardware—I’m in cloud-computing territory. Simply browsing websites or using a web app does not, by itself, describe the delivery model.

Cloud computing is commonly described using five essential characteristics (often referenced from the National Institute of Standards and Technology (NIST) definition):

On-demand self-service: I can provision resources as needed, without requiring a person at the provider to do it for me.
Broad network access: services are available over the network and can be accessed from different types of clients (laptops, phones, thin clients).
Resource pooling: provider resources are shared across multiple customers (multi-tenant), with resources assigned and reassigned based on demand (with logical separation between customers).
Rapid elasticity: capacity can scale out and scale in quickly to match demand—sometimes automatically.
Measured service: usage is metered so it can be monitored, controlled, and reported, giving transparency for both the provider and the consumer.

Cloud computing is not defined only by “it’s cheaper.” Cost efficiency is often a benefit, but the core shift is speed and flexibility: I can provision in minutes, experiment faster, and adjust capacity as needs change.

Finally, cloud computing comes with a shared responsibility mindset: the provider manages some parts, and I still manage others (especially my data and who can access it). How much I manage depends on whether I’m using IaaS, PaaS, or SaaS.

Practical Understanding

Practical Situation 1: “We use a browser, so we’re using cloud computing”

A team says they are “doing cloud” because they use web-based email and web apps. That might be true, but that statement alone isn’t a definition.

How to think about it: A browser tells me how I access something, not how the computing resources are delivered and managed. Cloud computing is about on-demand delivery of computing services and the ability to provision and scale those services without owning the underlying infrastructure.

Common misunderstanding: “Anything on the internet is cloud.” Not quite—cloud computing is a specific delivery model, not a synonym for the internet.

Practical Situation 2: “I need a server today, not next week”

A developer needs a Virtual Machine (VM) or database for testing and cannot wait for procurement or datacenter setup.

How to think about it: This points to On-demand self-service: I can provision what I need right now through a portal, Command-Line Interface (CLI), or API. If it’s a cloud service, I should also expect Measured service—usage is tracked so billing and visibility reflect what I consumed.

Common misunderstanding: “On-demand self-service means the system auto-scales.” No—this characteristic is about who/how provisioning happens, not about scaling behavior.

Practical Situation 3: “Traffic spikes, then drops back to normal”

An application has a big usage spike (campaign, seasonal peak) and then returns to normal levels.

How to think about it: This is Rapid elasticity: capacity can expand and shrink quickly to match demand. The key mental model is “scale out / scale in” without long lead times.

Common misunderstanding: “Rapid elasticity is the same as on-demand self-service.” They’re related, but different: one is about provisioning without provider interaction; the other is about fast scaling as demand changes.

Practical Situation 4: “We moved to IaaS, so the provider manages everything now”

A team migrates servers to a cloud provider and assumes they no longer manage anything.

How to think about it: Cloud uses a shared responsibility split. With IaaS, I still manage more (for example, what runs on my VMs, access, and my data). With PaaS, I manage less because the provider manages more of the platform. With SaaS, I manage the least, focusing mostly on configuration, users, and data governance.

Common misunderstanding: “IaaS eliminates IT work.” It reduces some work (like physical hardware), but it does not remove responsibility for applications, identities, and data.

Common Pitfalls

Mistake: Treating “using the internet” as the definition of cloud computing. Correction: Cloud computing is on-demand access to computing resources and services, not just internet connectivity.
Mistake: Assuming cloud computing always means public cloud. Correction: Cloud computing can be delivered through public, private, or hybrid approaches; the delivery model matters more than the location.
Mistake: Thinking cloud computing eliminates all IT management responsibilities. Correction: Responsibility is shared; what I manage changes by service model (IaaS vs. PaaS vs. SaaS), but I always retain responsibility for key areas like access and data.
Mistake: Believing cloud computing is only about cost savings. Correction: Cost can be a benefit, but cloud is often about speed, agility, and scaling—being able to move and adapt quickly.
Mistake: Mixing up “on-demand self-service” with “rapid elasticity.” Correction: On-demand self-service is about provisioning without provider interaction; rapid elasticity is about fast scaling out/in as demand changes.
Mistake: Interpreting “resource pooling” as “no isolation or security boundaries.” Correction: Resource pooling means shared provider capacity (multi-tenant) with logical separation; it does not mean “everyone shares the same data.”
Mistake: Assuming “measured service” means “cheap” or “fixed price.” Correction: Measured service means metering/monitoring/reporting usage for transparency and consumption-based billing.

Check Your Understanding

In one sentence, explain cloud computing without using the words “internet” or “server.”
Write the five essential characteristics in your own words, then add one “memory hook” for each.
Think of a product you use in a browser daily. What evidence would you need to decide whether it is delivered using a cloud computing model?
Describe a situation where rapid elasticity matters more than cost savings. What would go wrong without it?
For each service model (IaaS, PaaS, SaaS), write down one thing you still need to manage as a customer.