The term cloud is used as a metaphor for the Internet, based on how the Internet is depicted in computer network diagrams and is an abstraction for the complex infrastructure it conceals. Cloud or CloudComputing is a style of computing in which dynamically scalable and often virtualized resources are provided as a service over the Internet. Users need not have knowledge of, expertise in, or control over the technology infrastructure in the "cloud" that supports them.
How much does hosting in Google App Engine cost?
Its free to start, and allows up to 5 million page views per month which is more than enough to begin with! For full details on quotas and pricing please refer to Google App Engine site: code.google.com/appengine/docs/billing.html