Cloud computing, or just Cloud, is a delivery model in which IT resources and information are provided on demand from locations accessible via the Internet. They allow for use of computing resources on demand and for usage to flex as needs change. Cloud based resources can be made up from any type of IT provision that was traditionally provided from local server farms. Cloud delivery allows for unique service provision. Cloud services can be provided from Public Cloud providers that are available to everyone from shared infrastructure. They can be from Private Cloud providers who dedicate IT resources for specific organisations. Organisations can also build their own Private Cloud infrastructure. Many organisations adopt a Hybrid Cloud model that uses IT resources from a mixture of Public & Private Clouds, with Local on site IT provision. These resources are often made up of Software as a Service (SaaS), Platform as a Service (PaaS), and Infrastructure as a Service (IaaS) solutions.