Cloud computing is a large scale parallel and distributed computing system. It is a system which is consists of collection of interconnected and virtualised computing resources that are managed to be one or more unified computing resources. It opens up the world of computing to a broader range of uses and simplifies the use by providing access through any internet connection. It is a pay per use model which is available, convenient and is on demand network accessed to a shared pool of configurable computing resources like networks, servers, applications, services etc. It can be extensively provisioned and can be released with least management efforts or by a service provider interaction.