I was moving a key frame on the Z location in the graph editor along the X axis (horizontally) but the object was moving vertically on the Z axis. I thought because the value didn't change, the object wouldn't move.
What you have described sounds like the correct behavior.
If you are manipulating the Z location channel (or curve) in the graph editor (GE), then you are manipulating the up/down location even of you are moving it left and right in the GE.
You need to think about what is happening between your keyframes that you are shifting.
(maybe you are just moving the keyframe in the action editor? If so, take a look at what is happening in the GE)
Yes, it is the GE and now that you explained it and I looked at it again, it makes sense. I also moved the X keyframe and it only moved along the X. Thanks again for your timely response.
*I'm a retired teacher and I think your video lessons, planning, and pacing are done very well. Which is not easy to do in video format.