Cloud computing is the delivery of computing services—like servers, storage, databases, and software—over the internet. Instead of owning and maintaining your own computing infrastructure, you can access these services from a cloud provider like Amazon Web Services (AWS), Google Cloud, or Microsoft Azure.

Think of it like electricity. You don't build your own power plant to light your home. You plug into a grid managed by a power company and pay for what you use. The cloud works the same way for computing resources. It allows companies to rent access to everything from applications to storage, freeing them from the complex and costly task of managing their own hardware and software.

What makes a service a “cloud” service? A few key characteristics define it. These features work together to provide the flexibility and efficiency that make the cloud so powerful.

First is on-demand self-service. You can provision computing capabilities, such as server time or network storage, automatically without requiring human interaction with the service provider. Need more power? You can get it in minutes.

Next is broad network access. Services are available over the network and can be accessed through standard mechanisms by any type of device, like mobile phones, tablets, laptops, and workstations.

Cloud computing also relies on resource pooling. The provider's resources are pooled to serve multiple consumers using a multi-tenant model. You don't know or care exactly which physical machine is running your code; you just know it's running somewhere in the provider's vast data centers.

Perhaps the most famous feature is rapid elasticity. Resources can be scaled up or down quickly, and in some cases automatically, to match demand. If your website suddenly gets a surge of traffic, the cloud can allocate more resources to handle it. When traffic dies down, it scales back. This means you don't have to over-prepare for peak times.

Finally, cloud systems use a measured service. Resource usage is monitored, controlled, and reported, providing transparency for both the provider and the consumer. It's the foundation of the pay-as-you-go model, where you only pay for the resources you actually consume.

Cloud computing services come in three main models, each offering a different level of control and convenience. They are often abbreviated as IaaS, PaaS, and SaaS.

IaaS is the most flexible model. It gives you the raw building blocks of computing, like virtual servers and data storage. You're responsible for managing the applications, data, and operating systems, while the provider manages the physical hardware.

PaaS builds on top of IaaS. The provider manages not just the hardware but also the operating systems and middleware. This lets developers focus purely on building and running their applications without getting bogged down in infrastructure management.

SaaS is the most common model. It delivers a complete software product that the provider runs and manages. Users connect to the application over the internet, usually with a web browser. Examples include email services like Gmail, file storage like Dropbox, or office tools like Microsoft 365.

Just as there are different service models, there are also different ways to deploy cloud infrastructure. These are known as deployment models.

In a public cloud, you share the same hardware, storage, and network devices with other organizations or “tenants.”

The key is that the infrastructure is operated solely for a single organization, giving it more control and privacy.

This mixed environment gives businesses greater flexibility and more deployment options.

Why has cloud computing become so dominant? The advantages are significant.

Cost-Effectiveness: Cloud computing eliminates the capital expense of buying hardware and software and setting up and running on-site data centers. You trade capital expenses for variable expenses and only pay for IT as you consume it.

Scalability: With the cloud, you can scale elastically. This means delivering the right amount of IT resources—for example, more or less computing power, storage, and bandwidth—right when they are needed and from the right geographic location.

Performance: The biggest cloud computing services run on a worldwide network of secure data centers, which are regularly upgraded to the latest generation of fast and efficient computing hardware. This offers better performance than a single corporate data center.

Speed & Agility: Most cloud computing services are provided self-service and on-demand, so even large amounts of computing resources can be provisioned in minutes. This gives businesses a lot of flexibility and takes the pressure off capacity planning.

Reliability: Cloud computing makes data backup, disaster recovery, and business continuity easier and less expensive because data can be mirrored at multiple redundant sites on the cloud provider’s network.

These core concepts provide the foundation for understanding how cloud platforms like AWS operate and why they've become a fundamental part of modern technology.