Unaccusative...Unergative...Ergative...neep?

Hello All!!

I'm currently reading a book called "Events as Grammatical Objects" which is quite
interesting and very worthwhile if your interested in Syntax and other things.
Anyways, I'm a bit confused over the terms Unaccusative, Unergative and
Ergative all of which are used a lot in the book. I'm also interested in
knowing what they are...since I'm a linguistics major for god sakes! I mean,
shouldn't I know what these things are? :) Also, I think that an understanding
of the terms could help in making another breakthrough in understanding the
weirdness of several aspects of Silindion's verb structure which I was never
quite sure about. :) Thanks a lot for any help!

Elliott