I don't know how long you've been training for, how often you train, or what level you're at. I can only infer from your questions, that you are a beginner... aren't we all?
So anything I say may not make any sense to you. However, I can generally and safely say that all of these exercises deal with the forces of weight (gravity), the ground reaction force, and imaginary (read "vector") forces in 6 basic directions - front/back, left/right, up/down. It's how you use those forces to do the work that's the "key"... pun intended.
Although I agree with Adam to a point, that there is no right/wrong way to practice, and that any practice is better than no practice at all, I'd cæveat that by saying, at least by being cognizant of the *what* that is meant to be trained helps greatly.