Cloud computing is a service delivery and usage model, through the network in order to on-demand, easy to extend the way to get the required services. The core concept of cloud computing is through continuously improve the processing ability of the "cloud", and to reduce the processing burden on the end user, end user terminal is simplified into a simple input and output devices, and according to the need to enjoy the "cloud" of the powerful computing capabilities.
Cloud computing is a pattern to use pay. This model provides available, convenient, according to the requirements of network access, into allocation of computing resources shared pool (resources, including network, servers, storage, applications, service), these resources can be quickly provided, just put a few management work, and service providers with little interaction.
Cloud computing service consists of several levels: infrastructure as a service (IaaS), platform as a service (PaaS) and software as a service (SaaS).