Cloud computing is a general term for anything that involves delivering
hosted services over the Internet. These services are broadly divided
into three categories: Infrastructure-as-a-Service (IaaS),
Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). The name
cloud computing was inspired by the cloud symbol that's often used to
represent the Internet in flowcharts and diagrams.
A cloud service has three distinct characteristics that differentiate it
from traditional web hosting. It is sold on demand, typically by the
minute or the hour; it is elastic -- a user can have as much or as
little of a service as they want at any given time; and the service is
fully managed by the provider (the consumer needs nothing but a personal
computer and Internet access). Significant innovations in
virtualization and distributed computing, as well as improved access to
high-speed Internet, have accelerated interest in cloud computing.