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.