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.