Originally Posted by Venus

All I know is that it's a temporary stamp (if your approved on the spot) that serves as your green card while your waiting for the actually green card to show up in the mail. They only give it to you if you have some sort of emergency like your EAD is about to expire and you'll lose your job or you have a trip coming up that's outside of the USA. You have to have a urgent need for the stamp they won't give it to you just because you want a stamp on your passport.