The Key Concepts of Cloud Computing

we are bombarded daily with ads about products, white papers, publications, seminars, workshops, market projections and more focused on cloud computing. But if you analyze these messages you reach the conclusion there are many ambiguities and only a few emerging concrete terms.

For a start, cloud computing is not a technology but a model of provision and marketing IT services that meet certain characteristics. Cloud is all about computer services, not products:

* The infrastructure is shared. Multiple clients share a common technology platform and even a single application instance.

* The services are accessed on demand in units that vary by service. Units can be, for example, user, capacity, transaction or any combination thereof.

* Services are scalable. From the user's point of view, services are flexible; there are no limits to growth.

http://www.pcworld.com/businesscenter/article/200332/the_key_concepts_of_cloud_computing.html