Welcome, sspray, to this board. As you may notice, this board is truly dedicated to addicts-- those who have a need to cruise. We try to be friendly and helpful.
I don't know what the problem is between you and the first respondent who saw your post elsewhere. I just hope that you have come here to share with nice people, who really do like to help each other. If you are here to just help yourself, then you may be missing the point of this board.
First, onboard credit, is like the second respondent said--something offered by Carnival when problems happen that inconvenience all the passengers of the cruise. I recieved a 50% on another cruise after one of my cruises got caught up on a sandbar.
Like others have said, there are no freebies either . All coupons and offers from Carnival will require you to spend money. Now, the drink coupons that you can buy from Carnival can save maybe about 50 cents, or the price of the tip, if you drink the 4.95 drinks. And if you put out the money for that last bingo game, you can take a chance and win a free cruise. (but you have to put up 10 dollars (i think) for the bingo game (not free!!!!). Other than that, the only discounts are the deck/room UPGRADE you may get.
Good luck and best wishes on your cruise!!!
coffeecups