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PaaS is a cloud delivery option that sits on top of IaaS to enable companies to take advantage of a unified and abstracted way of developing and deploying applications. PaaS hides the complexity of the underlying computing services from IT practitioners in order to streamline the application development life cycle and deployment process. 

## Diving into Infrastructure as a Service 

IaaS, the most straightforward of the cloud delivery models, is the delivery of computing resources in the form of virtualized operating systems, workload management software, hardware, networking, and storage services. It may also include the delivery of operating systems and virtualization technology to manage the resources. 

IaaS provides compute power and storage services on demand. Instead of buying and installing the required resources in their traditional data center, companies rent these required resources as needed. This rental model can be implemented behind a company’s firewall or through a third-party service provider. See more information on renting in the section “Listing the characteristics of IaaS.” 

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Virtualization  is often used as a foundation of cloud computing. Virtualization separates resources and services from the underlying physical delivery environment. With this approach, you can create many virtual systems within a single physical system. A primary driver for virtualization is consolidating servers, which provides organizations with efficiency and potential cost savings. 

## Listing the characteristics of IaaS 

IaaS has two types of services: 

✓ A public service  is designed so consumers in any size business can acquire services in a rental model. Some public cloud services are open to anyone with a credit card that pays per use. Other public cloud services are contractual and provide a higher level of service to the buyer. 

