Depending on their deployment model, most cloud computing companies can be categorized as: Public cloud, Private cloud, or Hybrid cloud. Other categories include Community cloud, Distributed cloud, Intercloud, and Multicloud.
Public cloud is the one that most people think of when they talk about the cloud. Public cloud is hosted by a service provider who rents space on the cloud to its many customers, or tenants. Those customers generally only pay for services they actually use. Public cloud let you offload management where you don’t mind giving up some control. That’s why they are a popular choice for hosting everyday apps like email, Customer Relationship Management, HR, and other business support apps.
Private cloud is private because it only has one tenant. The single tenant can get all the goodness of a cloud, and can also control and customize it to fit the needs. And the control is why many companies are migrating their data centers to private clouds to run core business apps that provide unique competitive advantages like research, manufacturing, supply chain management, and more. Yet, private cloud still relies on on-premise IT rather than a third-party cloud provider. Managing a private cloud can be more expensive than owning on-premise infrastructures due to the additional cost of virtualization and cloud management. There are several cloud providers that can deploy private cloud infrastructures and thus lower the cost for enterprises.
Hybrid cloud is a combo of both private and public clouds. Users can create new innovative apps with uncertain demand. Apps the user can deploy on private cloud can burst to the public cloud during demand spikes.