Cloud computing has now become one of the rapidly growing technologies in computer science. Cloud Computing makes its greatest impact on the IT ecosystem. It refers to the delivery of services like hardware, software, storage and infrastructure over the internet. This is called the next generation of internet. The IT organizations, businesses and other customers can take the required services and resources from cloud quickly, easily and at affordable cost (pay as u go fashion). This paper describes the basic architecture, types and models of cloud computing it also gives us a comparative study of various clouds given by different providers. The comparison is simply based upon number of factors like products, services, languages support and many other parameters of clouds.