Section 9.1 of the eighth grade California Physical Science book talks about five very important things. This section touches on Motion, reference points, distance, displacement and vector. Motion is an action or process of moving or of changing place or position. Motion can even be a bodily movement or change of position or a gesture. Therefore if an object is in motion its distance from another object is changing.
Reference points are important in judging motion because they give us a specific point of to help us determine if an object is moving or not. Therefore on object is in motion if it changes positions relative to its reference points. Objects that are stationary such as a tree, building or flagpole make the best reference points. An example of the use of reference points would be if a person is riding in a car he can pick a reference point such as a tree and then determine that the car is in motion because the tree is getting closer. To take things a little further, using reference points you can then indicate change of position by plus or minus. These signs can stand for any pair of opposing directions from a reference point. This could mean right and left, up and down, away from and toward or in front of and behind.
There is also relative motion. Relative motion is whether or not an object is in motion so it depends on its reference point. An example of relative motion could be a group of sky divers jumping from a plane. The relative motion from the plane would make it seem that the plane is not moving but the sky divers are moving away from the plane towards the ground. If the relative motion was from the sky diver, it would appear that the plane is moving away and the sky divers were not moving but the ground is getting closer.
Furthermore we come to distance and displacement. When something moves distance between the reference points change. So the distance in the length of the path between the two points. Then there is...