Cloud Computing is the delivery of Information Technology services and solutions within delivery models that are characterised in their exhibition of five key facets: User driven service control, resource elasticity, device/location agnosticism, unit based & metered usage & billing, and utilisation of shared computer, network & storage resources.
Several delivery models that determine the nature of Cloud services exist, defining technical, management, tenancy, ownership and responsibility domains and boundaries. In addition, multiple service models exist that determine the types of services that can be consumed based on the level of readiness exhibited by a given service.
Delivery models include: Private Cloud, Public Cloud and Hybrid Cloud. Service models include: Software as a Service (SaaS), Platform as a Service (PaaS) and Infrastructure as a Service (IaaS).