Expanding businesses can scale the infrastructure in accordance with growth whilst private clouds (accessible only by the business itself) can protect the storage and transfer of the sensitive data that some businesses are required to handle.
Cloud hosting; the hosting of websites on virtual servers which are founded upon pooled resources from underlying physical servers.

Virtual Data Centers (VDC);  a virtualized network of interconnected virtual servers which can be used to offer enhanced cloud hosting capabilities, enterprise IT infrastructure or to integrate all of these operations within either a private or public cloud implementation.

Infrastructure as a Service is a provision model in which an organization can bank on Enormous,  the equipment used to support operations, including storage, hardware, servers and networking components. We  provide the equipment and is responsible for housing, running and maintaining it. The client typically pays on a per-use basis.

Scalability; resource is available as and when the client needs it and, therefore, there are no delays in expanding capacity or the wastage of unused capacity

No investment in hardware; the underlying physical hardware that supports an IaaS service is set up and maintained by the cloud provider, saving the time and cost of doing so on the client side

Utility style costing; the service can be accessed on demand and the client only pays for the resource that they actually use
Location independence; the service can usually be accessed from any location as long as there is an internet connection and the security protocol of the cloud allows it

Physical security of data centre locations; services available through a public cloud, or private clouds hosted externally with the cloud provider, benefit from the physical security afforded to the servers which are hosted within a data centre

No single point of failure; if one server or network switch, for example, were to fail, the broader service would be unaffected due to the remaining multitude of hardware resources and redundancy configurations.  For many services if one entire data center were to go offline, nevermind one server, the IaaS service could still run successfully.