Private cloud services are delivered from a business' data center to internal users. This model offers versatility and convenience, while preserving the management, control and security common to local data centers. Internal users may or may not be billed for services through IT chargeback.
In the public cloud model, a third-party provider delivers the cloud service over the internet. Public cloud services are sold on demand, typically by the minute or hour. Customers only pay for the CPU cycles, storage or bandwidth they consume. Leading public cloud providers include Amazon Web Services (AWS), Microsoft Azure, IBM SoftLayer and Google Compute Engine..
Hybrid cloud is a combination of public cloud services and on-premises private cloud -- with orchestration and automation between the two. Companies can run mission-critical workloads or sensitive applications on the private cloud while using the public cloud for bursting workloads that must scale on demand. The goal of hybrid cloud is to create a unified, automated, scalable environment that takes advantage of all that a public cloud infrastructure can provide while still maintaining control over mission-critical data.