A non-profit advocate of open cloud computing
Cloud Computing 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. The concept incorporates technologies that have the common theme of reliance on the Internet for satisfying the computing needs of the users. Cloud Computing services usually provide applications online that are accessed from a web browser, while the software and data are stored on the servers.
Companies or individuals engaging in Cloud Computing do not own the physical infrastructure hosting the software platform in question. Instead, they avoid capital expenditure by renting usage from a third-party provider (except for the case of 'Private Cloud' - see below). They consume resources as a service, paying instead for only the resources they use. Many Cloud Computing offerings have adopted the utility computing model, which is analogous to how traditional utilities like electricity are consumed, while others are billed on a subscription basis.