The cloud is a metaphor for the internet, the network of networks which makes it possible to easily send data from one place to another.
Cloud computing is the utilization of this
technology. Vendors allow businesses and individuals
to store data and use software on their servers,
saving their customers the cost of purchasing and
maintaining the equipment and services themselves.
Simply put, when someone says they're saving their files "on the cloud," they're saving their files to a server in an off-site, secured location, to be retrieved as quickly and easily as files stored on their computer's hard drive.