A basic question I have is what is the differenc between Orientation vs. the x,y,z, rotation. When I change the values they seem to do the same thing.
I remember adjusting Orientation for a 3D layer, then Rotation and ask people if they noticed any difference. Some people said they did notice a difference. That's complicated
Because, as you noticed, they do the same thing as you drag. The difference is not in the start and end states of the animation, but in how it goes from one to the other (this is, how it interpolates).. Orientation lends to smoother interpolation, since it goes through the shortest route from a combined XYZ set to the other. The three dimensions kind of collaborate with each other, if you want. Rotation X, Y and Z are more chaotic in nature, because they don't know what the others are doing. This means it's probably rougher many times, but also a ton of creative possibilities.
Also, Orientation goes back to zero when you go past 359.99 degrees. So one important aspect to the rotation propeties is that they allow revolutions, ie multiple turns.
WEIRD, Weird, Weird. If you move the Anchor Point using the Pan Behind Tool, the numbers change for the X, Y, Z values in the layer window, However if you undo the move and then type in those same numbers the Anchor point indicator stay put in the Comp window and the layer moves?????
Look again. Pan Behind doesn't just adjust anchor point, but also position. In fact, it modifies position so that the layer seems to remain in the same place. Confusing, huh?
Now do this: first create a motion path for a layer, then enable Auto-Orient (Control+Alt+O, not required but it will help) and then drag the anchor point values in the timeline. Is it more clear now that the layer is not changing position, but that it's kind of re-threading in the path? This is not so evident when a motion path isn't there, and that's why the layer seems to change position. It does so because anchor point defines which specific point is used to apply the position value.
In the example you just tried, using Pan Behind would produce unwanted changes in the motion path, because it adjusts both position and anchor point to visually make the layer stay in the same place as the anchor point moves.
This is all a bit confusing, I know. Let me know if it's still not clear (and take a look at the relevant pages in AE help).