The cloud computing is the computing which is completely based on the Internet. It can also be defined as the next stage in the evolution of the Internet. The cloud computing uses the cloud (Internet) that provides the way to deliver the services whenever and wherever the user of the cloud needs. Companies use the cloud computing to fulfill the needs of their customers, partners, and providers. The cloud computing includes vendors, partners, and business leaders as the three major contributors. The vendors are the one who provide applications and their related technology, infrastructure, hardware, and integration.

The partners are those who offer cloud services demand and provide support service to the customers. The business leaders are the ones who use or evaluate the cloud service provided by the partners. The cloud computing enables the companies to treat their resources as a pool and not as independent resources.

A cloud is a combination of hardware, networks, storage, services, and interfaces that helps in delivering computing as a service. It has broadly three users which are end user, business management user, and cloud service provider. The end user is the one who uses the services provided by the cloud. The business management user in the cloud takes the responsibility of the data and the services provided by the cloud. The cloud service provider is the one who takes care or is responsible for the maintenance of the IT assets of the cloud. The cloud acts as a common center for its users to fulfill their computing needs.

The four basic characteristics of cloud computing are given as follows:
• Elasticity and scalability.
• Self-service provisioning and automatic de-provisioning.
• Standardized interfaces.
• Billing self-service based usage model.

A cloud service is a service that is used to build cloud applications. This service provides the facility of using the cloud application without installing it on the computer. It reduces the maintenance and support of the application as compared to those applications that are not developed using the cloud service. The different kinds of users can use the application from the cloud service, which may be public or private application.

Some important features of the cloud service are given as follows:
• Accessing and managing the commercial software.
• Centralizing the activities of management of software in the Web environment.
• Developing applications that are capable of managing several clients.
• Centralizing the updating feature of software that eliminates the need of downloading the upgrades.