Delivering on the basic needs of the data center is Infrastructure as a Service (IaaS). IaaS provides the servers, network, storage, and bandwidth needed that are traditionally delivered through physical components in a corporate data center or hosting facility.
IaaS replaces the need to purchase infrastructure, provide maintenance, and deal with the life cycle of the physical infrastructure.
IaaS solutions can come in many shapes and forms (e.g., managed, self-service, short or long term, enterprise class, open source tools), but they are all delivered as a service, which means you pay a fee to use the infrastructure. Usage can be short or long term depending on your needs and the provider you choose.