The best example of virtualization, dynamic scalability and remote accessibility is cloud computing, which can include computers and servers from any corner of the world. Cloud computing can be defined as the capability of a scalable system (rather set of systems) that can provide abstraction between the technical architecture and the computing resources and also provide a capability to start services on-demand. The essential characteristics of cloud computing that distinguishes it from others are:

•    Measured service,
•    On-demand self-service,
•    Resource pooling,
•    Broad network access, and
•    Rapid elasticity.

Another term that is associated with cloud computing is data center. Today, the majority of infrastructures are deployed through it.  It mainly consists of five layers namely client, application, platform, infrastructure, and server layer.

The client in a cloud computing is the channel or resource used for the delivery of desired application or services.

Cloud application layer helps client to deliver the software as a service, which provides user the facility of accessing software which are not installed on local machine without actually installing it. This is a network based layer that provides management and access to available software.

The cloud platform layer provides facility to deliver the platform (computing platform) as a service. It also provides facility of software installation and management without worrying about the architecture.

The cloud infrastructure layer is used as a virtualized platform environment and delivers computer infrastructure as a service to the users. Clients generally prefer to buy infrastructure as an outsourced service rather than investing huge amount on such infrastructures like data center and servers.

The server layer consists of actual computer software and hardware products that can be used on cloud computing. This layer is used for computation and provides various other services.

The deployment of cloud computing can take one of the following models:

Public cloud : This is the cloud computing environment where the services are self-serviced on-demand and billed as per the utility computing.

Community cloud : This is the environment where infrastructure is shared among various community or organization with their consent. But this kind of arrangement at the same time requires higher security privacy and policy compliance and the cost is spread among all the communities.

Private cloud : This is a cloud computing within a closed network (a private network). The user still needs to buy some hardware and thus does not serve all the cloud computing purpose, but at the same time, ensures the privacy and compliance.

Hybrid cloud : This includes both the public and private architectures.