For many years the relationship of your Azure AD (AAD, recently called Microsoft Entra) tenant to the ahead tenant that your company uses was 1:1. Since around June, this is no longer a necessary prerequisite. Whether your company uses multiple Azure AD tenants due to a merger or via organizational constraints, they can now be brought together under a single ahead. Within ahead such different tenants are called Organizations.
Since you authenticate against a specific AAD tenant, that brings along some restrictions
That's it. That is the whole list.
ahead's internal representation of users means that you can search for people across all of the connected tenants. Through advanced targeting it is possible to target users across all tenants (e.g. a News for location equals Bern, regardless through which tenant the user logged in).
Here our intranet can really shine in that it can bring people from once disparate organizations together under one internal communications hub!