StratusCore (IaaS)
Network and server infrastructure provided as a private, public or hybrid virtualized environment. Rather than purchasing servers, data center space or network equipment, instead you buy those resources as a fully outsourced service. The service is typically billed on a utility computing basis and amount of resources consumed (and therefore the cost) will typically reflect the level of activity.
Private Cloud Services
The concept of a Private Computer Utility was first described by Douglas Parkhill in his 1966 book "The Challenge of the Computer Utility". The idea was based upon direct comparison with other industries (e.g. the electricity industry) and the extensive use of hybrid supply models to balance and mitigate risks.
Private cloud and internal cloud have been described as neologisms, however the concepts themselves pre-date the term cloud by 40 years. Even within modern utility industries, hybrid models still exist despite the formation of reasonably well functioning markets and the ability to combine multiple providers.
Some vendors have used the terms to describe offerings that emulate cloud computing on private networks. These (typically virtualisation automation) products offer the ability to deliver some benefits of cloud computing whilst mitigating some of the pitfalls. These offerings capitalise on data security, corporate governance, and reliability concerns during this time of transition from a product to a functioning service based industry supported by competitive marketplaces.
They have been criticized on the basis that users "still have to buy, build, and manage them" and as such do not benefit from lower up-front capital costs and less hands-on management, essentially "[lacking] the economic model that makes cloud computing such an intriguing concept
Public Cloud Services
Public cloud or external cloud describes cloud computing in the traditional mainstream sense, whereby resources are dynamically provisioned on a fine-grained, self-service basis over the Internet, via web applications/web services, from an off-site third-party provider who and bills on a fine-grained utility computing basis.
Hybrid Cloud Services
A hybrid cloud environment consisting of multiple internal and/or external providers "will be typical for most enterprises". By integrating multiple cloud services users may be able to ease the transition to public cloudservices while avoiding issues such as PCI compliance.
Another perspective on deploying a web application in the cloud is using Hybrid Web Hosting, where the hosting infrastructure is a mix between Cloud Hosting for the web server, and Managed dedicated server for the database server.