Things can appear to be moving, when they really aren’t. Sometimes an object might seem to be at rest, even when it is in motion. It’s all relative. Relative motion, that is. How things appear to move depends on how you, or any observer, happens to be moving. So, if you’re on a bus looking out a window into another bus, and your bus begins to back up slowly, you may think the other bus is moving forward, when really it’s not moving at all. That’s motion in motion. It happens all around us all the time.