Flash AS2 - Can't Understand _root.link

Hi,

I'm working on a menu bar and I found some code lines that might help me... thing is I don't understand few lines: _root.link != page and _root["btn" + _root.link]

Please help me if you can, I need this done right now

on (rollOver)
{
    if (_root.link != page) 
    {
        this.gotoAndPlay("over");
    }
}

Code (markup):

on (release)
{
	_root["btn" + _root.link].gotoAndPlay("out");
	_root.link = page;
}

Code (markup):

 

Possibilities

1. _root.link is the variable flsh player received from outside
2. _root.link is the last link clicked by the user and was recorded

page is the local variable in the movieclip button is in.

regards