UGN Security Forums UGN Security: Underground Off Topic what does redirgen.php do?

Hello to everyone this is my first post on this bbs.
This exploit here for IE:
http://www.securityfocus.com/archive/1/354447

Has something in its code that i dont understand.
What does the "redirgen.php?" part of the code do? Why is it used at that point what are its advantages?

I thought it was something similar to:
But its not isnt it!?

Thanks for Answers.

If you read the code it sais that it's triggered by executing another script (hence redirgen.php).