Bird watching project cont. Random Movement MX explanation tutorial?

Hi everyone!

Recently I applied this coding from http://www.kirupa.com/developer/mx/random_motionMX.htm to my bird watching skills development final year project (Getting birds to move randomly and pausing). I just want to know if there is a tutorial explaining each line or section of code and what it accomplishes for this tutorial.

I found an explanation for another random motion tutorial http://www.kirupa.com/developer/actionscript/random_motion2.htm but it seems to be quite different (layout and code)

I need to explain this in quite some detail in my log book so any comments on any part of the code for the top link etc would be appreciated. thanks for help you can give me!