Cloud Computing is one of the recent emerging technologies. In this word cloud refers to "Internet" which refers cloud computing as Internet-based computing.In this cloud computing different types of services like storage,applications and servers etc are provided to any organization through internet when demanded or needed. It uses the concept of traditional super computing also known as high-performance computing. It performs tens of trillions of computations per second. Generally the high-performance computing are used in military and research facilities. It is simply pay for use concept where the organisations pay for the services they use until they need it. The five basic characteristics of cloud computing are as follows:resource pooling,measured service,broad network access,rapid elasticity and on-demand self service. It also has three service models defined in it.They are namely Software as a service(SaaS),Platfom as a service(PaaS) and Infrastructure as a service(IaaS).The four main deployment models are private cloud,public cloud,hybrid cloud and community cloud.