Cloud computing is the combined use of computer technology ('computing') and the development of Internet-based ('cloud'). Cloud (cloud) is metefora from the internet, which is often depicted as clouds in
computer network diagrams. As the cloud in computer network diagrams, the cloud (cloud) in a Cloud Computing infrastructure is also an abstraction of the complex was hiding.
 It is a method of computing in which information technology-related capabilities provided as a service (as a service),
[2 ] so that users can access it via the Internet ("in the cloud")
 without knowing what was inside, an expert with it, or have control over the technology infrastructure that helped him.
 According to a paper published in 2008 IEEE Internet Computing "Cloud Computing is a paradigm in which information is permanently stored in servers on the Internet and temporarily stored on the user's computer (client) included in it is a desktop, tablet computers, notebooks, wall computers, handhelds, sensors, monitors and other .
Cloud computing is a concept that includes SaaS, Web 2.0, and other recent technology trends are well known, the common theme is reliance on the Internet to provide the computing needs of users. For example, Google Apps provides common business applications online that are accessed through a web browser with software and data stored on the server. Cloud computing is currently the latest technological trends, and examples of the development of Cloud Computing technology is iCloud
here's a breakdown of what the cloud computing :
1. SaaSThis type of cloud computing delivers a single application through the browser to thousands of customers using a multitenant architecture. On the customer side, it means no upfront investment in servers or software licensing; on the provider side, with just one app to maintain, costs are low compared to conventional hosting. Salesforce.com is by far the best-known example among enterprise applications, but SaaS is also common for HR apps and has even worked its way up the food chain to ERP, with players such as Workday. And who could have predicted the sudden rise of SaaS "desktop" applications, such as Google Apps and Zoho Office?
2. Utility computingThe idea is not new, but this form of cloud computing is getting new life from Amazon.com, Sun, IBM, and others who now offer storage and virtual servers that IT can access on demand. Early enterprise adopters mainly use utility computing for supplemental, non-mission-critical needs, but one day, they may replace parts of the datacenter. Other providers offer solutions that help IT create virtual datacenters from commodity servers, such as 3Tera's AppLogic and Cohesive Flexible Technologies' Elastic Server on Demand. Liquid Computing's LiquidQ offers similar capabilities, enabling IT to stitch together memory, I/O, storage, and computational capacity as a virtualized resource pool available over the network.
3. Web services in the cloudClosely related to SaaS, Web service providers offer APIs that enable developers to exploit functionality over the Internet, rather than delivering full-blown applications. They range from providers offering discrete business services -- such as Strike Iron and Xignite -- to the full range of APIs offered by Google Maps, ADP payroll processing, the U.S. Postal Service, Bloomberg, and even conventional credit card processing services.
4. Platform as a serviceAnother SaaS variation, this form of cloud computing delivers development environments as a service. You build your own applications that run on the provider's infrastructure and are delivered to your users via the Internet from the provider's servers. Like Legos, these services are constrained by the vendor's design and capabilities, so you don't get complete freedom, but you do get predictability and pre-integration. Prime examples include Salesforce.com's Force.com,Coghead and the new Google App Engine. For extremely lightweight development, cloud-based mashup platforms abound, such as Yahoo Pipes or Dapper.net.
5. MSP (managed service providers)One of the oldest forms of cloud computing, a managed service is basically an application exposed to IT rather than to end-users, such as a virus scanning service for e-mail or an application monitoring service (which Mercury, among others, provides). Managed security services delivered by SecureWorks, IBM, and Verizon fall into this category, as do such cloud-based anti-spam services as Postini, recently acquired by Google. Other offerings include desktop management services, such as those offered by CenterBeam or Everdream.
6. Service commerce platformsA hybrid of SaaS and MSP, this cloud computing service offers a service hub that users interact with. They're most common in trading environments, such as expense management systems that allow users to order travel or secretarial services from a common platform that then coordinates the service delivery and pricing within the specifications set by the user. Think of it as an automated service bureau. Well-known examples include Rearden Commerce and Ariba.
7. Internet integrationThe integration of cloud-based services is in its early days. OpSource, which mainly concerns itself with serving SaaS providers, recently introduced the OpSource Services Bus, which employs in-the-cloud integration technology from a little startup called Boomi. SaaS provider Workday recently acquired another player in this space, CapeClear, an ESB (enterprise service bus) provider that was edging toward b-to-b integration. Way ahead of its time, Grand Central -- which wanted to be a universal "bus in the cloud" to connect SaaS providers and provide integrated solutions to customers -- flamed out in 2005.
Today, with such cloud-based interconnection seldom in evidence, cloud computing might be more accurately described as "sky computing," with many isolated clouds of services which IT customers must plug into individually. On the other hand, as virtualization and SOA permeate the enterprise, the idea of loosely coupled services running on an agile, scalable infrastructure should eventually make every enterprise a node in the cloud. It's a long-running trend with a far-out horizon. But among big metatrends, cloud computing is the hardest one to argue with in the long term.
The Structure Model Of Cloud Computing :