"Cloud is a parallel and distribute d computing system consisting of a collection of

inter- connected and virtualized compute r s that are dynamically provisioned and present e d as one or more unified computing resources based on service- level agree m e n t s (SLA) established through negotiation betwee n the service provider and consume r s ."

"Clouds are a large pool of easily usable and accessible virtualized resources (such as hardwar e , developme n t platforms and/ or services). These resource s can be dynamically reconfigured to adjust to a variable load (scale), allowing also for an optimum resource utilization"