In cloud computing, software exists on top of the cloud infrastructure that allows one to build highly complex and robust applications. Quite often, though not necessarily, the "platform" used to build applications is also provided by the Cloud Service Provider (CSP).

The platform might be some kind of "cloud operating system" or even simpler technologies that enables services to be easily built and deployed, perhaps providing data storage and retrieval services, communication between service elements, etc. When the platform upon which applications may be built is provided by a service provider, it is usually referred to as a "Platform-as-a-Service" (PaaS) and the provider of such services is referred to as a Platform Service Provider (PSP).

One is usually not required to utilize existing platform services of a CSP. The user of a CSP may implement and deploy a different platform, including one that is created privately. Such a platform may provide the same kinds of services as a commercial PSP, though it would simply be referred to as an application platform.

See Also: Cloud Computing, Infrastructure-as-a-Service, Software-as-a-Service