Speaking of other models, the most basic cloud service model is called Infrastructure as a Service (IaaS). It's also the most similar to on-premises: you can think of IaaS as a way to have a virtual data center. As the name suggests, the cloud provider offers you a slice of the infrastructure they host, which consists of three types of resources:
- Compute, such as virtual machines, containers, or bare-metal machines (excluding operating systems)
- Networking, which aside from the network itself includes DNS servers, routing, and firewalls
- Storage, including backup and recovery capabilities
It's still up to you to provide all the software: operating systems, middleware, and your applications.
IaaS can be used in scenarios ranging from hosting websites (might be cheaper than traditional web hosting), through storage (for example, Amazon's S3 and Glacier services), to high-performance computing and big data analysis (requires huge computing...