What Is Cloud Computing?
Cloud computing is not a single piece of technology, like a microchip or a cellphone. Instead, it's a system primarily comprised of three services:
Software-as-a-service (SaaS) involves the licensure of a software application to customers. Licenses are provided through a pay-as-you-go model or on-demand. A popular example is Microsoft Office's 365.
Infrastructure-as-a-service (IaaS) involves a method for delivering everything from operating systems to servers and storage through IP-based connectivity as part of an on-demand service. Clients can avoid the need to purchase software or servers, and instead procure these resources in an outsourced, on-demand service. Examples of the IaaS system include IBM Cloud and Microsoft Azure and Amazon EC2, Rackspace.
Platform-as-a-service (PaaS) is considered the most complex of the three layers of cloud-based computing. PaaS shares some similarities with SaaS, the primary difference being that instead of delivering software online, it is a platform for creating software that is delivered via the Internet. This model includes platforms like Force.com and Heroku.