A few new classes in Flash 8 push it beyond previous versions by providing external communication with other technologies. Developers have been coding workaround external communication solutions for years, but this time Flash got it right with a few new classes, one of which is called ExternalInterface. This class provides an interface that allows direct communication between ActionScript and other languages.
External Communications with Flash 8: How to Use the ExternalInterface
Peachpit, Written by Kris Hadlock