if you read the flash docs and the openfl docs some of it is just lifted verbatim. I've never used AS3 ( or any other AS ) but I believe the correlation here would be AS3 Haxe and Flash OpenFL. I don't know how similar AS3 and Haxe are - but I've not needed that to learn Haxe so far - but OpenFL was originally based directly on Flash API as far as I know. And the doc shows it. But OpenFL has diverged in various places of course.