What are the layers in the SAP Cloud Platform Architecture?

The SAP Cloud Platform Architecture includes 3 layers and they are SaaS, PaaS and IaaS. 

Platform-as-a-service (PasS) is the SAP Cloud Platform service. Sofware-as-a-service extensions are on top of the platform such as SAP SuccessFactors, SAP Ariba, SAP S/4HANA, SAP Hybris and Concur. The platform requires an Infrastructure-as-a-service (IaaS) where the SAP DATA Center and third-party DATA Centers are located.