FSCommand is used to send message to the parent/host application. Parent or host application can be your Browser, Standalone-Flahs-Projector, or any other application enbeding the flash player control in it..
(Exec can execute any external .EXE file with argument)
Some of the FS Command actions are predefined in the swish menue for FS Command, but you can send your self-created FS Commands...
Suppose you have created a swish movie and it releases an FS Command on click of a button, and that command is not used in flash projector (.EXE) nor the browser can understand it, then how to use it?