For the last several years, the market has been evolving towards on-demand infrastructure provisioned on a flexible, pay-as-you-go basis, but the introduction of cloud computing offerings has radically accelerated innovation in this market. The economic downturn has accelerated adoption of these offerings, thanks to the cost-savings that can be achieved by the move from physical to virtual services, and from purchasing for peak capacity to obtaining what you need only when you need it. The majority of hosting customers now obtain at least some of their infrastructure on-demand, and most new hosting contracts include on-demand services. This evolution has quickly changed the vendor landscape, bringing many new entrants to rapid prominence, as well as decreasing the relevance of hosters who have failed to make this shift. According to Gartner, cloud computing is “a style of computing in which massively scalable IT resources are delivered as a service to one or multiple customers using Internet technologies.
Elastically scalable cloud-computing resources are distributed dynamically and are redistributed on demand in metered quantity and quality. Delivery "as a service" implies that the base of the resources is off-premises relative to the consumer of the service — that is, the term "as a service" implies that it is off-premises.”
Obtain what you need only when you need it!