Confused about the differences of WA AD and WA ACS

Hi folks,

I am really confused about not getting the clear difference of Windows Azure Active Directory and Windows Azure Access Control Services. I reached the point multiple times where I thought I got it but then I found another blog article and......

Is WA AD just another IP (identity provider) which can be use in WA ACS? If it so I don't understand the naming of the "module" in the management portal which is named "Active Directory" but where we can create new ACS namespaces.

Or is WA AD the same as WA ACS like documentation of the Access Control Service 2.0 describes: "Windows Azure Active Directory Access Control (also known as Access Control Service or ACS) is a cloud-based service..." (http://msdn.microsoft.com/library/gg429786.aspx).

PLEASE HELP! I am missing the big picture!

Thanks from Germany,

Tobias Jamin