There are a number of cloud service models that can be divided into four separate categories: Business Process-as-a-Service, Software/Application-as-a-Service, Platform-as-a-Service and Infrastructure-as-a-Service
Business Process-as-a-Service (BPaaS) is in fact any type of horizontal or vertical business process that is delivered through cloud services. It is usually automated, allowing businesses to consume outcomes without the need to actually own any of the assets. BPaaS reduces labor count through increased automation, thus also cutting costs in the process. Solutions are delivered via Web-centric Service Integration on shared infrastructures that can be used by multiple customers.
Software/Application-as-a-Service (SaaS) is a way of delivering applications over the Internet. It is also called Web-based software, on-demand software, or hosted software. Customers can access from multiple client devises different applications without having to purchase expensive software and hardware and eliminating the need for creating complex management processes.
Platform-as-a-Service (PaaS) provides all the infrastructure needed to develop and run applications over the Internet. In other words, it is a way to rent hardware, operating systems, storage and network capacity over the Internet. This way, IT departments can focus on innovation and product development, rather than create and maintain complex infrastructure.
Infrastructure-as-a-Service (IaaS) is a form of cloud-based service, where consumers use all the computing resourves needed to support operations, such as storage, servers and networks. Just as in any other type of cloud services, consumers are not required to own any of the assets, but they pay for using those provided on shared, multi-tenant infrastructures.
Depending on the type of business and its preferences, the suitable cloud services could be private, public or hybrid.
Public cloud services are rendered over a network that can be used publicly. A services provider offers all the resources, such as servers and storage and consumers can rent them over a period of time to use.
Private cloud services essentially have the same architecture and are designed to offer the same features as public cloud but these are provided to an individual enterprise and are protected by a corporate firewall.
There could be a middle ground, of course, and this is where hybrid cloud services come in handy. They can combine various features from private and public service models to meet the specific needs of every organization. In hybrid services external and internal delivery methods can be integrated.