The ApplicationDomain class is a container for discrete groups of class definitions. Application domains are used to partition classes that are in the same security domain. They allow multiple definitions of the same class to exist and allow children to reuse parent definitions. Application domains are used when an external SWF file is loaded through the Loader class. All ActionScript 3.0 definitions in the loaded SWF file are stored in the application domain, which is specified by the applicationDomain property of the LoaderContext object that you pass as a context parameter of the Loader object's load() or loadBytes() method. The LoaderInfo object also contains an applicationDomain property, which is read-only.


The LoaderContext class provides options for loading SWF files and other media by using the Loader class. The LoaderContext class is used as the context parameter in the load() and loadBytes() methods of the Loader class. When loading SWF files with the Loader.load() method, you have two decisions to make: into which security domain the loaded SWF file should be placed, and into which application domain within that security domain? For more details on these choices, see the applicationDomain and securityDomain properties.


The SecurityDomain class represents the current security "sandbox," also known as a security domain. By passing an instance of this class to Loader.load(), you can request that loaded media be placed in a particular sandbox.


The System class contains properties related to local settings and operations. Among these are settings for camers and microphones, operations with shared objects and the use of the Clipboard.