The Flash Player API classes are in the flash.* packages. The Flash Player API refers to all packages, classes, functions, properties, constants, events, and errors that are in the flash package. They are unique to Flash Player, as opposed to the top-level classes, such as Date, Math, and XML, or the language elements, which are based on ECMAScript. The Flash Player API contains features that you expect to find in object-oriented programming languages, such as the flash.geom package for geometry classes, as well as features specific to the needs of rich Internet applications, such as the flash.filters package for expressiveness and the package for handling data transmission to and from a server.

 Top Level 
 flash.accessibilityThe flash.accessibility package contains classes for supporting accessibility in Flash content and applications.
 flash.dataThe package contains classes used for working with Adobe AIR local SQL databases.
 flash.desktopThe flash.desktop package contains classes used for copy-and-paste and drag-and-drop operations, as well as the Icon class, used to define system icons used by a file.
 flash.displayThe flash.display package contains the core classes that the Flash Player uses to build visual displays.
 flash.display3DThe flash.display3D package contains the classes that the Flash Player uses to render geometrically defined graphics.
 flash.display3D.texturesThe flash.display3D.textures package contains classes for textures.
 flash.errorsThe flash.errors package contains a set of commonly used error classes.
 flash.eventsThe package supports the new DOM event model and includes the EventDispatcher base class.
 flash.externalThe flash.external package contains the ExternalInterface class which can be used to communicate with the Flash Player's container.
 flash.filesystemThe flash.filesystem package contains classes used in accessing the filesystem. This package is only available to content running in the AIR runtime.
 flash.filtersThe flash.filters package contains classes for bitmap filter effects.
 flash.geomThe flash.geom package contains geometry classes, such as points, rectangles and transformation matrixes, to support the BitmapData class and the bitmap caching feature.
 flash.htmlThe flash.html package contains classes used for including HTML content in an AIR application. This package is only available to content running in the AIR runtime.
 flash.mediaThe package contains classes for working with multimedia assets such as sound and video.
 flash.netThe package contains classes for sending and receiving from the network, such as URL downloading and Flash Remoting. 
 flash.printingThe flash.printing package contains classes for printing Flash-based content.
 flash.profilerThe flash.profiler package contains functions used for debugging and profiling ActionScript code.
 flash.securityThe package includes classes for validating XML signatures. This package is only available to content running in the AIR runtime.
 flash.systemThe flash.system package contains classes for accessing system-level functionality, such as security, multilanguage content, etc.
 flash.textThe flash.text package contains classes for working with text fields, text formatting, text metrics, style sheets, and layout.
 flash.text.engineThe FTE provides low-level support for sophisticated control of text metrics, formatting, and bi-directional text. While it can be used to create and manage simple text elements, the FTE is primarily designed as a foundation for developers to create text-handling components.
 flash.uiThe flash.ui package contains user interface classes, such as classes for interacting with the mouse and keyboard.
 flash.utilsThe flash.utils package contains utility classes, such as data structures like ByteArray.
 flash.xmlThe flash.xml package contains Flash Player's legacy XML support, and other Flash Player-specific XML functionality.