In traditional cel animation or flip-book animation, you create the illusion of movement by showing a series of images, each slightly different from the rest, simulating snapshots of the movement. When you create each of these drawings and place them in a series of keyframes, that process is called frame-by-frame animation. When you create only the most crucial snapshots and allow Flash to interpolate the minor changes that take place between those changes, you’re creating tweened animation. You learn more about tweening in Chapters 9 and 10.
A classic example of frame-by-frame animation is a bouncing ball. You can create a crude bouncing ball in just three frames.