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 Microsoft, Amazon, or Google.

Think of it like electricity. You don't build your own power plant at home. You just plug into the grid and pay for what you use. Cloud computing applies the same model to technology resources.

This model has several key characteristics that set it apart from traditional on-premises IT:

• On-demand self-service: You can provision computing resources like server time or network storage automatically, without needing human interaction with the service provider.
• Broad network access: Capabilities are available over the network and accessed through standard mechanisms by various clients, like laptops, mobile phones, and tablets.
• Resource pooling: The provider's resources are pooled to serve multiple customers using a multi-tenant model. Physical and virtual resources are dynamically assigned and reassigned according to demand. You generally have no control or knowledge over the exact location of the provided resources.
• Rapid elasticity: You can scale resources up or down quickly, and in some cases automatically, to match demand. To the customer, the resources available often appear to be unlimited.
• Measured service: Cloud systems automatically control and optimise resource use by leveraging a metering capability. Resource usage can be monitored, controlled, and reported, providing transparency for both the provider and the consumer.

Cloud services are typically categorised into three main models. Each model represents a different level of management and control over your computing resources. Understanding these helps you choose the right service for your needs.

Infrastructure as a Service (IaaS) is the most basic category. You rent IT infrastructure—servers, virtual machines, storage, networks—from a cloud provider on a pay-as-you-go basis. It’s like leasing a plot of land where you can build anything you want. You manage the applications, data, runtime, middleware, and operating system.

Platform as a Service (PaaS) provides an on-demand environment for developing, testing, delivering, and managing software applications. PaaS is designed to make it easier for developers to quickly create web or mobile apps, without worrying about setting up or managing the underlying infrastructure of servers, storage, network, and databases needed for development.

Software as a Service (SaaS) is a method for delivering software applications over the Internet, on demand and typically on a subscription basis. With SaaS, cloud providers host and manage the software application and underlying infrastructure and handle any maintenance, like software upgrades and security patching. Users connect to the application over the internet, usually with a web browser.

Beyond the service models, you also need to decide how your cloud infrastructure will be deployed. There are three main ways to deploy cloud services.

With a public cloud, all hardware, software, and other supporting infrastructure is owned and managed by the cloud provider. You access these services and manage your account using a web browser. The key benefits are lower costs, no maintenance, and near-unlimited scalability.

In a private cloud, the services and infrastructure are maintained on a private network. This model offers more flexibility and control, as the organisation can customise its environment. However, it also comes with the management responsibilities and costs of on-premises IT.

Hybrid cloud gives businesses greater flexibility and more deployment options. For example, you could use the public cloud for high-volume, lower-security needs like web-based email, and the private cloud for sensitive, business-critical operations. This is often called "cloud bursting," where an application runs in the private cloud but "bursts" to the public cloud when demand for computing capacity spikes.

Ready to test your knowledge? Let's see what you've learned about the fundamentals of cloud computing.

With these foundational concepts in place, you're ready to explore how Microsoft Azure implements these models to offer a vast array of services.