The cloud service that allows businesses to rent IT infrastructure instead of buying it is known as Infrastructure as a Service (IaaS). With IaaS, organizations can access virtualized computing resources such as servers, storage, and networking over the internet. This model eliminates the need for companies to invest in and maintain physical hardware, allowing them to scale resources as needed quickly. IaaS provides flexibility, reduces operational costs, and enables businesses to focus on their core competencies while leaving infrastructure management to cloud providers.