When an ActionScript program runs, the Flash runtime reads compiled ActionScript
bytecode and translates it into native machine-code instructions that are executed by
the specific computer hardware on which the program is running. In many cases, the
native machine-code instructions are saved so they can be used again without the
need to be retranslated from ActionScript bytecode.
Just as converting ActionScript 3.0 code to bytecode is called compiling, the process
of translating ActionScript bytecode into native machine code and then saving that
machine code for later execution is, likewise, known as compiling. Hence, most
ActionScript code undergoes two levels of compilation. First, the developer compiles
the code from human-readable format to a format understood by the Flash runtime
(ActionScript bytecode). Then, the Flash runtime automatically compiles the Action-
Script bytecode to a format understood by the hardware running the program (native