Platform as a Service (PaaS) is a service model of cloud computing, which provides hardware architecture, runtime libraries, operating system, and set of software subsystems or other components needed to perform a task.
PaaS providers allow users to develop design software using tools, OS, or libraries. One who creates the software has control on configuration settings and deployment. Moreover, networks, storage, web servers, and other required services are offered to host the user application. It facilitates the easy and cost-effective deployment of applications without the need for investing capital on hardware and software.
In simpler terms, PaaS allows user to rent virtualized servers, hardware, storage, operating systems, and network capacity over the network to develop and test new applications or for running existing applications. This service model benefits developer in many ways, such as it allows modifying / upgrading operating system features as per their requirements.
There are myriad of service providers that offer application hosting and a deployment platform, including several add-on services to the users, such as: application development, security, team collaboration, scalability, persistence, application versioning, marshalling, application instrumentation, All the services may differ as per the scalability and maintenance levels.
Broadly, there are five type of Platform as a Service, such as Add-on development facilities, Stand alone development environments, Application delivery-only environments, Open platform as a service, and Mobile PaaS (mPaaS).