AO moves the focal point of the image from the objective lens(es) forward and back to make the focus point fall on the focal plane of the reticle (crosshairs). Then, they will move together, no matter if your eye is directly behind them or not.
Quote:The Objective lens focuses the target to the reticle. Exactly.
The ocular (eyepiece) adjustment is used to focus the image on the crosshair plane. Two different things.
Quote:the eye piece is the diopter end, it focuses your eye to the reticle Yep.
Here's a way to understand it:
If you look at a dial, like a clock, and the hands are 1 foot from the numbers, you'll need to be directly in front of it to read an accurate time.
Now, if you make the hands tight to the numbers, you can look at it from (almost) any angle and see an accurate time.
Parallax is shortening/lengthening the distance of the hands.
Stupid explanation, I know, but it's easy to understand and remember.
The ocular adjustment would be putting on glasses so you can read the numbers from across the room. 
