What do you have so far? While we at allnurses don't mind helping with homework related questions, we don't do all the work for you. Show us what you have and where you're stuck. You should have a basic pathophysiology textbook that should help you get started.
There are so many different types it and classifications, would take an hour to write it all out. Basically heart pump, pump goes bad, fluid back up to breathy thingies, and red fluid no come out as much from pump.