"Cloud" is a metaphor for the Internet and is an abstraction for the complex infrastructure it conceals. "Computing" refers to computer technology.
Cloud Computing refers to internet-based development that uses computer technology to provide software as a service (SaaS).
According to the IEEE Computer Society, "It is a paradigm in which information is permanently stored in servers on the Internet and cached temporarily on clients that include desktops, entertainment centers, table computers, notebooks, wall computers, handhelds, etc."
My comment is although there are some differences but I think this technology existed years ago but now they have just renamed it and packaged it in a more standard way e.g. UDDI existed years ago to provide web services globally to client applications.
For instance, Google few years ago introduced Google Docs and some other cloud tools, but it's good that Microsoft finally decided to invest on this.