Action Script 3.0 (AS3) is Adobe's programming language. It is used in the applications Flash and Flex to develop interactive web applications, interactive animations and games.
AS3 is a complete and fully functional object-oriented programming language which can handle a vast array of interactivity-related tasks such as handling key stroke and mouse click events to playing video and audio to handling AR input via a webcam. Moreover, since AS3 is part of the Flash platform it is fully integrated with Flash's drawing and animating capabilities and therefore allows referencing pre-made art and objects in your very simple.
So what's the catch, you ask? The catch is that AS3 is not the easiest programming language to learn. But never fear, Adobe is here for you.
One of the very best places to begin learning AS3 is a series of videos presented on Adobe TV: Actionscript 1:1 with Doug Winnie. In nearly 50 short videos, Doug takes you through AS3 programming step-by-step. By the time you're half way through you'll know enough to begin developing your own games. Check out Doug's videos and start creating your own interactive media.