Infrastructure as a Service (IaaS)
IaaS model, considered the most basic cloud service model, is used to provide pre-provisioned virtual resources, which can be a server, a database or an application. In this model, providers offer computers – either virtual or physical machines - in addition to other resources. This also allows leveraging existing assets to provide resources with high availability, strong security and excellent reliability.

Platform as a Service (PaaS)
In his model, cloud providers deliver a computing platform which includes operating system, programming language, execution environment, database, and web server. This permits developing of applications on a cloud platform without the cost and complexity of buying and managing the underlying hardware and software layers.

Software as a Service (SaaS)
In the Saas model, cloud providers install and operate application software in the cloud, and users access the software from cloud clients. Furthermore, cloud users do not manage the cloud infrastructure and platform on which the application is running. This eliminates the need for installing and running the application on the cloud user's own computers simplifying maintenance and support.