Cloud computing is the delivery of computing and storage capacity  as a service  to a heterogeneous community of end-recipients. The name comes from the use of a cloud-shaped symbol as an abstraction for the complex infrastructure it contains in system diagrams. Cloud computing entrusts services with a user's data, software and computation over a network.
There are three types of cloud computing:
Using Infrastructure as a Service, users rent use of servers (as many as needed during the rental period) provided by one or more cloud providers.
Using Platform as a Service, users rent use of servers and the system software to use in them.
Using Software as a Service, users also rent application software and databases. The cloud providers manage the infrastructure and platforms on which the applications run.
End users access cloud-based applications through a web browser or a light-weight desktop or mobile app while the business software and user's data are stored on servers at a remote location.
Proponents claim that cloud computing allows enterprises to get their applications up and running faster, with improved manageability and less maintenance, and enables IT to more rapidly adjust resources to meet fluctuating and unpredictable business demand.
Cloud computing relies on sharing of resources to achieve coherence and economies of scale similar to a utility (like theelectricity grid) over a network (typically the Internet). At the foundation of cloud computing is the broader concept of converged infrastructure and shared services.