When I learned that even NATO embraced cloud computing I was really surprised, well, maybe it is time to get a closer look at this.
The most correct definition so far is:
"Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction." - from National Institute of Standards and Technology (NIST)
The term "cloud" is used as a metaphor for the Internet, based on the cloud drawing used in the past to represent the telephone network,and later to depict the Internet in computer network diagrams as an abstraction of the underlying infrastructure it represents. Typical cloud computing providers deliver common business applications online that are accessed from another Web service or software like a Web browser, while the software and data are stored on servers.
Additional information:
What is Cloud Computing?
Cloud Computing Deep Dive - Free Special Report (PDF)
