Cloud delivery models are models that represent the computing environments. These are as follows:
Infrastructure as a Service (IaaS) : Infrastructure as a Service (IaaS) is the delivery of services, including an operating system, storage, networking, and various utility software elements, on a request basis.
Platform as a Service (PaaS) : Platform as a Service (PaaS) is a mechanism for combining Infrastructure as a Service with an abstracted set of middleware services, software development, and deployment tools. These allow the organization to have a consistent way to create and deploy applications on a cloud or on-premises environment.
Software as a Service (SaaS) : Software as a Service (SaaS) is a business application created and hosted by a provider in a multi-tenant model.
Function as a Service (FaaS) : Function as a Service (FaaS) gives a platform for customers to build, manage and run app functionalities without the difficulty of maintaining infrastructure. One can thus achieve a "serverless" architecture.