excerpt a pictorial representation of the motion of an object. it usually takes the form of a one- or two-dimensional plot showing the position of the object at defined times. Generally, the times are equally spaced, and one can tell at a glance whether an object is remaining at a constant velocity, or if it is accelerating. One can obtain the average velocity between two such marked positions by measuring the distance between these positions and dividing by the time interval between them.
a motion diagram commonly shows position at each position, but it might also show the velocity with an attached vector at each position, allowing you to determine the average acceleration between positions easily.