Think of a Flash movie as having two dimensions. For example, an image might appear in the top-right corner of the movie in the first frame, move to the centre over the course of the next 20 frames, then disappear in frame 30. Of course, because Flash movies are interactive, they do not always play through the timeline automatically. Often the user determines the action by clicking buttons or making other choices. The second dimension of a Flash movie is its layers.
Layers determine which objects appear in foreground and which are pushed to the back.
The logo would have to be on top to be seen. Suppose you want to create a whimsical animation of a heart swelling with love. You would create a heart symbol and place one in frame one and then a copy in, say, frame 10. Using the editing tools, you would modify the image in frame 10 to look like it has fully bulged. Finally, the tweening command instructs the computer to move gradually from the original heart to the bulging heart over the course of the 10 frames.