What Is IaaS, PaaS, And SaaS?

The National Institute of Standards and Technology (NIST) recognizes three standard cloud computing models of as-a-service: Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS), and Software-as-a-Service (SaaS). 

In effect, each of these models offers a progressive level of abstraction – or management – by the cloud provider.