Hypers: also called reverse hypers and roman chairs. It's where you have a pad on your thighs and behind your ankles where you can do a reverse sit-up motion.
Powercleans: yes it is like the clean and jerk just without the overhead press. Also they are usually done without dipping at the knees, so that the end of the motion is at the full upright instead of having to dip and front squat the weight up. Thus the difference between full cleans and powercleans.
Cheers,
Scotsman