ActionScript is a object-oriented programming language for the Adobe Flash Player and Adobe AIR runtime environments which is originally developed by Macromedia Inc. and now dissolved into Adobe Systems.
It is a derivation of HyperTalk, the scripting language for HyperCard. It is now a dialect of ECMAScript (a superset of the syntax and semantics of the language more widely known as JavaScript).
ActionScript 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 for games, interactive animations, tutorials, tools etc. ActionScript 3 is also used with Adobe AIR system for the development of desktop and mobile applications.
The language itself is open-source in that its specification is offered free of charge and both an open source compiler (as part of Apache Flex) and open source virtual machine (Mozilla Tamarin) are available.