One of the things I've personally found the most confusing about SharePoint is that it isn't a single product. It's kind of a Windows thing (Windows SharePoint Services), but it's also kind of an Office thing (Microsoft Office SharePoint Server). Then there's things like SharePoint Portal Server (which I'm assuming is the product now called SharePoint Server for Search?) to help add to the possible confusion. Lots of renames both inside and outside the product only helps to add to the confusion.
All that said, there's at least one nice page that both tries to make it clear what SharePoint options there are, and at the same time give you a nice comparison of what each of them do and don't include in terms of capability. I have to admit, this one page at least clarified a lot of the questions I personally had about differences among the products, and it's great to have something that at least is trying to clarify these things for customers (and co-workers! 🙂