Cloud computing is Internet-based computing, whereby shared resources, software and information are provided to computers and other devices on-demand, like the electricity grid. It is a paradigm shift following the shift from mainframe to client–server that preceded it in the early 1980s.
Details are abstracted from the users who no longer have need of expertise in, or control over the technology infrastructure "in the cloud" that supports them.
Cloud computing describes a new supplement, consumption and delivery model for IT services based on the Internet, and it typically involves the provision of dynamically scalable and often virtualized resources as a service over the Internet.
It is a byproduct and consequence of the ease-of-access to remote computing sites provided by the Internet.