flash has what we call a hiercahy (if i spelled that right)
In order to refer to a specific MC when doing code, you have to type out it's path.
_root.mc1.mc2.etc
It's like a system of folders on a computer. C:/ is the _root (I dont know PC's very well, so excuse me if i mess something up with the C:/gbl/adgh/etc) and then you can refer to specific files or folders by doing /this/that
only in flash it's . instead of /, just like many other scripting/programming languages