A couple of weeks ago, I was presenting Project Online to a group of people, who are more from the SharePoint Community than Microsoft Project. Their knowledge of Project, Project Server was more
as users than IT Professionals.

Midway through the presentation we got into the discussion about various options that Microsoft is now offering as part of Office 365 and also the standard on-premises offerings for Project Portfolio Management.

Needless to say, that the discussion escalated quickly to a confusing array of terminology with Project Online, Project Pro for Office 365, Project Professional 2013 and what connects to what, what you can purchase how and so on. I was able to answer the questions, and also point the group to various excellent articles and references Microsoft put together on these topics.

Nevertheless, it occurred to me that it may not just be that one group that is confused with all the new offerings. So, I decided to put together a quick Info graph trying to explain various options available, and how they interact with each other.
I have made it available on TechNet Gallery so that more people can come across it. 
You can download it from the TechNet Gallery by clicking on the image or from this direct link: in jpeg format here. Quick Reference Info-Graph for Project Online and Project Server 2013
Hope it is useful! If you find any errata, please do not hesitate to contact me.