PaaS refers to the underlying hardware and lower-layer software facilities provided by the cloud. In this case, the end user simply uses a provider's data center hardware, OS, middleware, and assorted frameworks to host their private application or services. Middleware may be composed of database systems. Many industries have been built using cloud provider commodity hardware such as Swedbank, Trek Bicycles, and Toshiba. Examples of public PaaS providers are IBM Bluemix, Google App Engine, and Microsoft Azure. The value of a PaaS deployment versus IaaS is the fact that you get the benefits of scalability and OPEX with a cloud infrastructure, but you also have proven middleware and operating systems from the provider. This is the realm of systems such as Docker where software is deployed as containers. If your overall application stays within the constraints of the vendor provided framework, and infrastructure  you can achieve a faster time to market since most of the componentry, OS, and middleware are guaranteed to be available.