References in functions?

Hi

I’m pretty new to actionscript, so This question might sound stupid but here it comes:

When you in a function pass a reference e.g: “private function test (argument:Sprite)…” does flash copy the sprite into the function which in my opinion would take a lot of time, or does it simply paste a reference? Actually we could compare it to a filesystem, does it copy the directory and name, or does it copy the whole file?

I am sure it must be the first, but I just wanted to be absolutely sure:D

Thanks in advance