This represents the animation princliple exageration. Notice how the characters eyes are hugh compared to the rest of the head. This puts a lot of attention on the eyes.
Secondary action refers to the action that is a result of another. For example when a gun fires the action is the bullet leaving the barrel, but you notice the slide on the gun is pushed back by the force given off by the gunpowder.
Spacing and Timing
Timing is inportant in animation to make it more realistic. When the ships jet burner fires there is a split second before it starts to move forward. This is timing to show the small time lag betweet the bootsers fireing and the actual thrust created.