When representing movement in Animation, it is important to consider the Physical attributes of the object or character represented. Is your CHARACTER heavy or light, is it rigid, semi rigid or flexible, does it move quickly or slowly. All those things, combined with each other, result in an interesting character (interesting to your eye, entertaining for your perceptive brain, now you can begin to understand why children love animation).

If you can imagine a still graphic indicating the position of your object across time, you will be able to make very important observations, that would help you understand the representation of Weight and Speed, and the basic relation between those 2 elements and the necessary deformation of objects though the movement, in order to produce an organic, interesting animation.