Cloud computing is the delivery of computing services — including servers, storage, databases, networking, software, and analytics — over the internet. Rather than owning and maintaining physical data centers, organizations rent access to these resources from a cloud provider and pay only for what they use.
This model shifts the burden of infrastructure management away from individual businesses and onto specialized providers who operate at global scale. The result is faster innovation, greater flexibility, and significant cost efficiency for organizations of all sizes.
Cloud computing is typically described using three core delivery models:
- Infrastructure as a Service (IaaS): Provides virtualized computing resources such as virtual machines, storage, and networking. The customer manages the operating system and applications, while the provider manages the physical hardware.
- Platform as a Service (PaaS): Provides a managed environment for building and deploying applications. The provider handles the infrastructure and runtime, freeing developers to focus purely on code.
- Software as a Service (SaaS): Delivers fully managed applications over the internet. The customer simply uses the software without managing anything beneath the application layer.
Alongside these service models, cloud computing is deployed in three primary configurations. A public cloud is owned and operated by a third-party provider and shared across multiple customers. A private cloud is dedicated infrastructure operated for a single organization, either on-premises or hosted by a provider. A hybrid cloud combines public and private environments, allowing organizations to keep sensitive workloads on private infrastructure while using the public cloud for scalable or less sensitive tasks.
Five essential characteristics define cloud computing according to widely accepted industry definitions: on-demand self-service, broad network access, resource pooling, rapid elasticity, and measured service. These characteristics are what separate true cloud computing from simply renting dedicated hardware remotely.
Understanding these foundational models and characteristics is the starting point for everything that follows in Azure. Every service you encounter in Azure maps to one of these models, and every deployment decision you make will reflect a choice among these configurations.
A regional healthcare provider previously managed its own data centers to host patient record systems. Server procurement took months, and capacity planning was often inaccurate — either over-provisioned and wasteful or under-provisioned and slow during peak periods. By migrating to a public cloud using IaaS, the provider now provisions servers in minutes and scales capacity automatically during periods of high demand such as flu season. Sensitive patient data that must remain on-premises stays in a private cloud, while analytics workloads run in the public cloud — a hybrid cloud configuration tailored to regulatory requirements.
- Cloud computing delivers computing resources over the internet on a pay-as-you-go basis.
- The three service models are IaaS, PaaS, and SaaS, each offering a different level of management responsibility.
- Deployment configurations include public, private, and hybrid clouds.
- Five characteristics define cloud computing: on-demand self-service, broad network access, resource pooling, rapid elasticity, and measured service.
- Every Azure service maps to one of these models, making this framework essential for understanding the platform.