The National Institute of Standards and Technology (NIST) (www.nist.gov) defines the following five important characteristics as the essence of cloud computing:
On-demand self service: Consumers of computing utility can provision and deprovision resources on the fly. The provisioning action can happen unilaterally in a self-serve manner without any human intervention with the service provider. For example, cloud computing has made it possible for an organization to provision a Hadoop cluster of a desired configuration from a console in their office, without having to call Amazon and letting them know about it.
Broad network access: The self-service part of cloud computing is facilitated via the Internet, allowing heterogeneous clients ranging from mobile phones to desktop computers to interact with the cloud computing service. Standard communication protocols such as HTTP are used to allow communication between these diverse sets of clients and the service...