Azure subscriptions and AAD tenants

Hi,

Can someone please explain the relation between Azure subscriptions and Azure Active Directory tenants.

What I noticed:

1. AAD tenant can exist without subscription. I noticed this when I logged in to portal.azure.com with my @hotmail.com email account.
2. When subscription is created (for example if I create a new Azure account) a tenant is created automatically.

I also noticed that when I tried to create another subscription I had to specify directory which as I understand in this case means AAD tenant.

This makes me think that multiple subscriptions may be linked to one tenant.

At the same time I can create multiple AAD tenants but it is not clear for me how AAD tenants are correlated to subscriptions.

I would highly appreciate if someone could clarify that for me.