When a Flash movie plays, it starts in frame 1 and continues to play each frame until it gets to the last frame, then it starts again in frame 1 and plays continuously.
We create animation by having different content in some of the frames, just like a movie. The frames where the content changes are called keyframes.
If you movie has movie clips inside other movie clips each movie clip plays along its own timeline. It is best to put all animation inside its own movie clip.
There are several ways of creating animation. We will explore several tools that make animation easier.