The PaaS model (Platform-as-a-Service or Platform as a Service)

In the platform-as-a-service (PaaS) model, the vendor provides a development environment for application developers, who develop software and offer those services through the
vendor's platform.

The vendor typically develops toolkits and standards for development and provides the distribution and payment channels. The provider typically receives payment for
providing the platform and the sales and distribution services. This enables the rapid spread of software applications, given the low cost of entry and the saturation of established channels
for customer acquisition.

PaaS is a variation of SaaS so the development environment is offered as a service. Developers use the vendor's tools (for example, predefined blocks of code) to create their own applications.

PaaS solutions are development platforms for which the development tool itself is hosted in the cloud and can be accessed through a browser. With PaaS, developers can often build web applications, without installing any tools on their computer, and the applications can be deployed without any specialized systems administration knowledge.

PaaS systems are useful because they allow developers to release web applications without the cost or complexity of purchasing servers and configuring them.

The benefits of PaaS are to dramatically increase the number of people who can develop, maintain, and release web applications. In short, PaaS offers a platform for the development of web applications.

At a minimum, a PaaS solution should include the following elements:

PaaS features
PaaS must use the web as infrastructure.
PaaS must provide an integrated development environment (IDE) such that developer applications run their applications in identical development and production environments.
PaaS must provide integration with external web services and databases.
PaaS should provide comprehensive application and user activity monitoring, to help developers understand their applications and user behavior.
Paas must be scalable, reliable, and secure without requiring additional development, configuration, or other costs.
Paas must have the ability to automatically partition state and data to serve an arbitrary number of users.