Recently i found a great video that describes What is Cloud Computing , What is Cloud server ?
the answer is inside the Video.. enjoy it.. :D
And these are the difference Among Cloud server and Virtual Private Server and Dedicated server
Cloud hosting offers many advantages over normal VPS or Semi-Dedicated server hosting services due to the number of servers that are being used for a single cluster, and if you or your business rely greatly on your website, Cloud hosting is the best suitable option for you. The enhanced architecture powering Cloud hosting solution utilize groups of high specification servers, network attached storage devices to reliably serve every web page, and image of a website. Inside each storage device, drives are replicated to each other in a RAID configuration to create a first level of redundancy.
With Virtual Private server, you will not get guaranteed resources that you will pay for, which means other user of the VPS node could squeeze in on your allotted resources but this is not case with Cloud server, you will get the guaranteed amount of resources you are paying for and it's always available when you need them. In addition to all these features, you will also get the ability to customize the resources of Cloud server anytime. VPS is not at all reliable when compared to Cloud server because VPS is based on software virtualization platform. Each platform of servers have their merits and demerits but here there are no demerits of Cloud server, so now it depends on you whether to choose VPS or Cloud server after understanding the needs and the service that you are looking.
While cloud hosting is starting to gain momentum, dedicated servers have been the backbone of hosting for years. Dedicated servers are ideal for websites that demand a high level of disk space and bandwidth, as well as businesses that need flexibility and customization in their servers. Unlike cloud hosting, dedicated servers reside in only one physical location.
With dedicated server hosting, a server is leased by the individual client and not shared with any other users. Dedicated hosting offers extreme flexibility, since none of the hardware or software is shared, allowing the end user to have ultimate control over features, such as software and the preferred operating system. The hosting company can also provide maintenance of the server, usually as an add-on service.
The level of support available obviously varies with the service plan, but dedicated hosting typically includes updated patches, which protect information on the server against hackers.
If you are considering dedicated hosting, keep in mind there is no set standard for dedicated service providers to follow. Although each dedicated service provider may use the same standard terms, the way each defines them will likely differ.
For instance, some providers may view a fully managed server as one with a control panel that is web based. Others may see it, however, as providing system engineers who are dedicated to all network and server components and operations of the provider.