There are Azure Stack, Private/Public/Hybrid Cloud in In Microsoft Azure.

Private Cloud: Azure on premise. An enterprise has to keep some apps and data on premise by regulations.

Public Cloud: Cloud hosted by Microsoft.

Hybrid Cloud: An enterprise uses both private and public cloud.

Azure Stack: in fact, it’s a private cloud. All the VMs, containers, app services, etc., are compatible and transferable seamlessly to public cloud if needed.