ActionScript 2.0 is a scripting language used by the Adobe Flash software, introduced in Flash MX 2004.
ActionScript is an object-oriented language originally developed by Macromedia Inc. (now owned by Adobe Systems). It is a dialect of ECMAScript (meaning it has a superset of the syntax and semantics of the more widely known JavaScript), and is used primarily for the development of websites and software targeting the Adobe Flash Player platform, used on Web pages in the form of embedded SWF files.
Flash MX 2004 introduced ActionScript 2.0, a scripting programming language more suited to the development of Flash applications.
References:
https://en.wikipedia.org/wiki/ActionScript#Timeline_by_ActionScript_version