Cloud computing is defined in the Gartner Information Technology Glossary as:
a style of computing in which scalable and elastic IT-enabled capabilities are delivered as a service using internet technologies.
It can range from “low level” infrastructure as a service to higher-level functions “as a service” to full applications (software as a service).
As our own Jeff Huber puts it,
“Cloud” just means your computer is at somebody else’s house.