Kirkll, maby I can help you out with Jason's quote.
When you draw a bow you put a certain amount of stored energy into it (the area under the draw force curve). When you releace that bow the stored energy goes into the KE of the arrow moveing forword, the KE of the limb, string, scilencers going forword, vibrations, ect... The efficiency of a bow is how much of that stored energy in put into the arrow.
So, you can have two bows both with the same draw force curve, both at the same final draw weight, both shooting the same arrow. One may have heavier limbs, string, have more vibratin, ect... it will shoot the arrow slower due to not being as efficient.
I bet it will be as clear as mud now!