Infrastructure as a Service (IaaS) in its most basic sense it is the delivery of computer infrastructure as a service instead of a product; kind of like "renting your computer equipment." Similar to SaaS and PaaS, IaaS is a provision model in which a
vendor outsources the equipment used to support operations (including data storage and hardware equipment such as servers and networking components) and the client pays on a per-use
vendor or service provider owns the equipment and is responsible for housing,
running and maintaining it, while the client pays for it and uses it to support business operations.
The original term was Hardware as a Service (HaaS), first coined by the
economist Nicholas Carr in March 2006, it is now more commonly known as Infrastructure as a Service (IaaS). The service is billed on a utility computing basis and so the cost depends on the amount
of resources consumed and the level of activity. It is an evolution of Web hosting and VPNs.