What is LUD?

Can anybody kindly tell me what is LUD?
Here is the current information of my case. How can I know which is LUD? Thanks

Application Type: I485, APPLICATION TO REGISTER PERMANENT RESIDENCE OR TO ADJUST STATUS

Current Status: Document OTHER THAN CARD manufactured and mailed.

On November 06, 2006, we mailed the document we manufactured based on our earlier approval of this case, and mailed it to the address on we have on file. You should receive the new document within 30 days. If you do not, or if you move before you get it, call customer service