AS is short for Action Script which is the flash programming language. All our files are made using actionscript and the only flash files that won't use it are plain timeline animation files. There are currently 3 versions of action script, 1.0, 2.0 and 3.0. The first is too primitive and has been used long time ago, therefore it's no longer being used. Things started to heat up when Macromedia Flash 8 was launched along with Actionscript 2.0 which allowed programmers to start building amazing flash components. Along with Flash CS3 Actionscript 3.0 was launched, it's more strict and precise but the code runs much faster and frameworks like Papervision 3D were made possible. After the launch of CS4 you could make 3D components in action script with the included 3D classes and no need for a third party framework like P3D. AS2 is easier to use and more loose, however for the advanced user we'd recommend AS3.