Short for Platform as a Service, PaaS is defined as a computing platform being delivered as a service. Here the platform is outsourced in place of a company or data center purchasing and managing their own hardware and software layers. Typically, PaaS facilitates deployment of applications, application development, testing, and also supports the building, testing and hosting of Web applications. PaaS enables IT to develop, test, deploy, host, and also update from a single streamlined environment. May also be referred to as cloudware.
Sun Microsystems identifies Platform as a Service (PaaS)as one of three layers of cloud computing, in addition to Software as a Service (SaaS) and Infrastructure as a Service (IaaS).