-- Distance is the length of a trip, with the twists, turns, and circle-backs all straightened out. The more times you run around a circular track, the greater distance you cover.
-- Displacement is the distance and direction from the start-point to the end-point, regardless of the route that was followed along the way. If you run once around a circular track, your displacement is zero, because your start-point and end-point are in the same place.
