When software designers, network architects, system designers, and other assorted technical geeks draw pictures of networks they use the cloud symbol to represent wide area networks. More specifically, in many network diagrams, they use the cloud symbol to represent the most famous wide area network of them all, the Internet. Companies have been trying, with varying degrees of success, to provide wide area network (AOL and CompuServe) and Internet based (MobileMe, Yahoo, and MSN) services for decades.
With the introduction of mobile computing platforms (phones and tablets), a real need for Internet based services has finally arrived, and since the marketing folks want consumers to distinguish these needed services from the previous efforts to provide unneeded services, they have decided to call them cloud-based services.
So in answer to the question, iCloud is nothing more than Apple's marketing, or brand name, for its Internet based services. Specifically, iCloud provides...