Programming language
Initially focused on animation, early versions of Flash content offered few interactivity features and thus had very limited scripting capability.
More recent versions include ActionScript, a scripting language which has syntax similar to JavaScript and so supporting JSON syntax (a variation on ECMA), but a much different programming framework and set of class libraries. ActionScript is used to create almost all of the interactivity (buttons, text entry fields, pick lists) seen in many Flash applications.
New versions of the Flash Player and authoring tool have striven to improve on scripting capabilities. Flash MX 2004 introduced ActionScript 2.0, a scripting programming language more suited to the development of Flash applications. As seen in the image to the right, it's often possible to save a lot of time by scripting something rather than animating it, which usually also retains a higher level of editability.
Of late, the Flash libraries are being used with the XML capabilities of the browser to render rich content in the browser. Since Flash provides more comprehensive support for vector graphics than the browser and because it provides a scripting language geared towards interactive animations, it is being considered a viable addition to the capabilities of a browser. This technology, which is currently in its nascent stage, is known as Asynchronous Flash and XML, much like AJAX, but with possibly greater potential.
Content protection
Many times, Flash authors will decide that while they desire the advantages that Flash affords them in the areas of animation and interactivity, they do not wish to expose their images and/or code to the world. However, once an .swf file is saved locally, it may then quite easily be decompiled into its source code and assets. Some decompilers are capable of nearly full reconstruction of the original source file, down to the actual code that was used during creation.
In opposition to the decompilers, SWF obfuscators have been introduced to provide a modicum of security, some produced by decompiler authors themselves. The higher-quality obfuscators use traps for the decompilers, making some fail, but none have definitively been shown to protect all content.