A cloud service model that delivers the computing platform (operating system and associated services) as a service over the internet by the provider.
With PaaS, companies develop their own software applications to run on a vendor’s application-hosting environment (the platform). The vendor provides and controls the programming languages, libraries, operating system, tools and services as well as the infrastructure resources, while customers focus on the applications themselves. Examples of PaaS include Salesforce and the Google App Engine.