Azure Active Directory has always been sort of just there. I've never paid any attention to the concept of Azure Active Directory tenants until last week. Azure AD was just an idea when we first started our Azure work 8 years ago. There were all kinds of "you can't do that in Azure AD" wrappers around it back then. Azure AD has grown in flexibility. Not it is time to look at the multi-tenancy aspects of Azure AD.
You can spend years in Azure without running across the tenancy.
• Got a personal Azure account? One tenant is plenty.
• Got an MSDN Azure subscription tied to your account? One tenant is plenty.
• Working in a corporate environment where some other group manages AD and provides your subscriptions? One tenant might be all you ever use.
We can walk through an example account to get a better understanding of Azure AD tenants why we might use them.