Here's the first ActionScript tutorial that explains about the way Flash works. This series explains Flash to people who already have a basic understanding of ActionSript.

Chapter 9: The display system
24 pages.
This chapter will explain how the stage is organized. Here you will learn how to add and remove elements from the stage and the differences between ActionScript 2.0 and 3.0.

Last: [link] (https://doom-the-wolf.deviantart.com/art/AS-Tutorial-Ch-8-Events-217519369)
Next:
ActionScript 2.0 elements (https://doom-the-wolf.deviantart.com/art/AS-Tutorial-Ch-10-AS2-Items-244261068)