What is Cloud computing?


Cloud computing is a category of computing solutions in which a technology and/or service lets users access computing resources on demand, as needed, whether the resources are physical or virtual, dedicated, or shared, and no matter how they are accessed (via a direct connection, LAN, WAN, or the Internet).

The cloud is often characterized by self-service interfaces that let customers acquire resources when needed and as long as needed. Cloud is also the concept behind an approach to building IT services that takes advantage of the growing power of servers and virtualization technologies.


Cloud computing's importance rests in the cloud's potential to save investment costs in infrastructure, to save time in application development and deployment, and to save resource allocation overhead.



What's the difference between a private and a public cloud? And what about hybrids? 


In general, a public (external) cloud is an environment that exists outside a company's firewall. It can be a service offered by a third-party vendor. It could also be referred to as a shared or multi-tenanted, virtualized infrastructure managed by means of a self-service portal.


A private (internal) cloud reproduces the delivery models of a public cloud and does so behind a firewall for the exclusive benefit of an organization and its customers. The self-service management interface is still in place while the IT infrastructure resources being collected are internal.


In a hybrid cloud environment, external services are leveraged to extend or supplement an internal cloud.



Is cloud computing the same as Software-as-a-Service? Infrastructure-as-a-Service? Platform-as-a-Service?


A growing number of people in the industry consider Software-as-a-Service (SaaS) -- software applications delivered over the Web -- to be a subset of cloud computing. And you could probably say the same thing about IaaS (remotely accessible server and storage capacity) and PaaS (lets developers build and deploy Web applications on a hosted infrastructure).


Where can I learn more about cloud computing? Start with IBM’s Resources and Events tab for technical articles, tutorials, demos, and other resources.