On-demand self-service. A consumer [of cloud services] can unilaterally provision computing capabilities, such as server time and network storage, as needed, automatically without requiring human interaction with each service provider.
Read: Get what you want, when you want it, with little fuss.
Broad network access. Capabilities are available over the network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g., mobile phones, tablets, laptops and workstations).
Read: Anyone, anywhere can access anything you build for them.
Resource pooling. The provider’s computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand.
Read: Economies of scale on galactic proportions.
Measured service. Cloud systems automatically control and optimize resource usage by providing a metering capability as appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled and reported, providing transparency for both the provider and consumer of the utilized service.
Read: Get what you want, when you want it, then give it back … and only pay for what you use.
Rapid elasticity. Capabilities can be elastically provisioned and released, in some cases automatically, to scale rapidly outward and inward commensurate with demand. To the consumer, the capabilities available for provisioning often appear unlimited and can be appropriated in any quantity at any time.
Read: Get what you want, when you want it … then give it back.
Each of these five characteristics must be present, or it is just not a cloud service, regardless of what a vendor may claim. Now that public cloud services exist that fully meet this cloud computing definition, you — the consumer of cloud services — can log onto one of the cloud service providers’ dashboards and order up X units of compute capacity, Y units of storage capacity and toss in other services and capabilities as needed. Your IT team is not provisioning any of the hardware, building images, etc., and this all happens within minutes vs. the weeks it would normally take in a conventional on-premise scenario.