You should get most of these answers online if you google them. However...just to recap in a simple way:
OBIEE is Oracle BI Enterprise Edition, their flagship BI product that competes with other tools like Cognos, Business Objects.
OBIEE Plus, OBIEE FOundations Suite..is usually a fancy name for a "Package" of things like OBIEE + Essbase, etc...
Hyperion/EPM is a separate product set but as of OBIEE 11g, Essbase Cubes are better integrated with OBIEE as a reporting platform.