Virtualization is software that separates physical infrastructure from the servers (or, in some cases, routers) to create various dedicated platform resources. Virtualization software enables a hosting provider run multiple operating systems and multiple applications on the same server at the same time, in partitioned allocations of memory -- making servers, desktop environments, data storage and file systems independent of the physical hardware layer.
Cloud computing can be thought of as the service that results from the application of virutalization, when those virtual resources do not require human intervention to be enabled, and are accessed via the internet. The so-called "cloud" is the availability of shared resources, software, or data — as an on-demand service via the Internet.
The cloud most often includes virtualization resources to deliver the service or services. The cloud provides a self-service capability, elasticity, automated management, scalability, and pay-as you go service that is not in place with virtualization out-of-the-box.
At larger organizations, data center consolidation and modernization might result in so-called "private" clouds.
Sofware-as-a-service (SAAS) lets anyone enjoy software applications (such as
Workbench "Always on the Job!"©) by licensing user "seats" on that is deployed by a provider, usually delivered in the browser or via a tablet or smart phone. The provider maintains the hardware and software, upgrades facilities and fixes problems -- users' total cost is lowered by eliminating deployment of the application in an organization's data center. SaaS applications are accessed over the Internet.
Virtualization is a technology that allows one or more physical server to appear to applications as multiple "logical platforms." These platforms can be accessed via the Internet, with automated tools, making them "Cloud" based.
