What are the 3 components that make up Cloud Computing?
Software as a service that SaaS - that is the say a software applications delivered from a remote multi tenanted infrastructure but still providing the same functionality that you would have if you ran your own hardware and software solution server based solutions without the need for a server.
Virtulisation - virtulisation enables the decoupling of hardware from the operating systems and applications. This enables far higher efficiently and reliability of the hardware platform capable of running multiple companies applications in their own discreet environment.
Utility computing - that enables dynamic server capacity across a grid infrastructure enabling you so scale on demand eliminating server upgrades.