What law or theory can explain the idea that if you are standing on a Earth, satellites move quickly but if you are standing on another satellite they stay still?

Law of Inertia.

Explanation:

In the absence of gravity, a satellite would move in a straight line path tangent to the Earth, while in the absence of any forces, an object in motion such a satellite would continue in motion with the same speed and direction.

answer; in the disk but not the halo;