A form of cloud computing that helps enterprise developers quickly write and text customer- or employee-facing Web applications that center around one development language or methodology. This means developers don't have to create on just any platform but can rather select one that matches their preferences in tools and language, such as .Net, Java, or Ruby on Rails.
The platforms promise more efficient coding through automation of tasks such as setting up a newly composed app as a Web service. Most also offer a cloudinfrastructure (or links to vendors such as Amazon.com) so that developers can launch what they build in a cloud infrastructure that can keep up with demand for the new application. In other words, the appeal of the Platform as a Service approach is that you develop using the same standards and technologies as the application will run under in production. This means cutting out the messy migration of moving an application off a Windows development box and into its target production environment. Debugging also occurs in an environmnet equal to the target production environment, leading to a surer resolution of bugs. And according to Charles Babcock of Information Week, it promises faster development. As of 2010 PaaS is still at an early stage.