Cloud computing refers to the use of Internet based computer technology for a variety of services. The purpose of this paper is to make us understand the types of clouds and its revolutionary impact on today’s dominant models. Now days, there is a huge increased focus on cloud computing as it enables easy access to servers, databases, application servers and storage. Cloud computing technology helped organizations to develop a unique business model using an infrastructure that can be reused remotely. With cloud computing the unit of computing has emerged itself as the data centre. It is a revolutionary contribution to the software industry as it reduced the complexity of accessing and using resources by introducing new software and systems. The Author takes us through the types of clouds, their contributions, the challenges associated with cloud computing technologies and the importance of scalability and flexibility in a cloud-based environment, siting examples like the Amazon EC2 services, Googles MapReduce, The Eucalyptus systems, Hadoop Distributed File systems.