Cloud Computing is becoming one of the next industry buzz words as industry big player such as Google, Amazon are following their old trend to chip in the newest technology. Cloud computing is Internet-based computing, whereby shared resources, software and information are provided to computers and other devices on-demand, like a public utility. Cloud computing is a general term for anything that involves delivering hosted services over the Internet. The cloud is a virtualization of resources that maintains and manages itself. In general, cloud computing customers do not own the physical infrastructure, instead avoiding capital expenditure by renting usage from a third-party provider. They consume resources as a service and pay only for resources that they use. These services are broadly divided into three categories

• Infrastructure-as-a-Service (IaaS)
• Platform-as-a-Service (PaaS)
• Software-as-a-Service (SaaS)

Infrastructure-as-a-Service (IAAS) - IAAS provides virtual server instances with unique IP addresses and blocks of storage on demand. Providers supply with application program interface (API) which user use it to start, stop, access and configure their virtual servers and storage. In the enterprise, cloud computing allows a company to pay for only as much capacity as is needed, and bring more online as soon as required. This is like pay what you use model.

Platform-as-a-Service (PAAS) - PAAS in the cloud is defined as a set of software and product development tools hosted on the provider's infrastructure. Developers create applications on the provider's platform over the Internet. PaaS providers may use APIs, website portals or gateway software installed on the customer's computer. Developers need to know that currently, there are not standards for interoperability or data portability in the cloud. Some providers will not allow software created by their customers to be moved off the provider's platform.

Software-as-a-Service (SAAS) - In the software-as-a-service cloud model, the vendor supplies the hardware infrastructure, the software product and interacts with the user through a front-end portal. SaaS is a very broad market. Services can be anything from Web-based email to inventory control and database processing. Because the service provider hosts both the application and the data, the end user is free to use the service from anywhere.

Some of the key features of cloud computing are

• Multi-tenancy
• Security
• Device and location Independence
• Cost
• Agility
• Reliability
• Scalability
• Maintenance
• Metering