The cloud was always used to describe something big and complex, something that cannot be painted on a presentation slide because the details are either too complex, unknown or simply not important. However, there are two different approaches to define Cloud Computing. The first approach is to define Cloud Computing as something that is delivered over a cloud, which in this case is the Internet. The second is to define the delivering IT systems, namely the datacenter itself as being the cloud.
“Cloud Computing refers to both, the applications delivered as services over the Internet, and the hardware and systems software in the datacenters that provide those services”. Vaquero (2009) says that “clouds are a large pool of easily usable and accessible virtualized resources (such as hardware, development platforms and/or services). These resources can be dynamically reconfigured to adjust to a variable load (scale), allowing also for an optimum resource utilization.”
On the other hand, and this is in the opinion of the author, the best matching definition of Cloud Computing comes from Stanoevska-Slabeva (2009), who says that “Cloud Computing is a phenomenon that comprises a number of aspects and is related to a new paradigm of IT delivery and deployment. Generally, Cloud Computing concerns the delivery of IT capabilities to external customers, or, from the perspective of the user, obtaining IT capabilities from an external provider, as a service in a pay-per-use manner and over the Internet.”
 Armbrust, M; et. Al. (2010), p.1
 Vaquero, L.M.; et. Al. (2009), p.15
 Stanoevska-Slabeva, K. (2009), p.49