Application functionality question

1

Hi there.
Just a simple query really. I would like to fully understand the functionality of a friends application he built using Flash. He made me aware that he used an open source Flash file for the interactivity of this file. Whilst riffling through it, i noticed part of actionscript code that seemed alien to the nature of the application. For example:

on (release)
{
    _parent.city.ty = 185;
    _parent.city.change = "yes";
    _parent.golf.change = "no";
    _parent.mount.change = "no";
    _parent.yacht.change = "no";
    _parent.city_sub.gotoAndStop(1);
    _parent.golf_sub.gotoAndStop(1);
    _parent.beach_sub.gotoAndPlay(2);
    _parent.mount_sub.gotoAndStop(1);
    _parent.yacht_sub.gotoAndStop(1);
}

this chunk of code ensures the list of destinations are displayed under its respective button after it has been pressed. If i change the all of the ‘yacht’, ‘beach’, ‘mount’ and so on, the list fails to appear. I would like to know how the

_parent.city_sub.gotoAndStop(1);
_parent.golf_sub.gotoAndStop(1);
_parent.beach_sub.gotoAndPlay(2);
_parent.mount_sub.gotoAndStop(1);
_parent.yacht_sub.gotoAndStop(1)

statements manipulate the lists, and weather the names like ‘yacht’, ‘beach’, ‘mount’ and so on, can be changed into more suitable words like ‘buildings’, ‘parking’, ‘misc’ and so on, to suit the theme of the application.

If need be, the file i am working on can be accessed here:
http://intasp.bcuc.ac.uk/20527796/interactive_campus_map_final.fla

Any help with this issue will be greatly appreciated, thank you!