Alright, this is going to be rather spoily so read at your own risk!
Well, at the begining of the film the whole gain (meaning the people who said "Aye!" at the end of the second movie) are at Singapore trying to get maps or "charts" on how to sail to World's End. It ends up becoming this big huge fight scene where you find out that Will has made a deal with Sao Feng (Chinese pirate) to trade Jack for the charts. World's End is in a sense a purgatory for people who are still being judged whether or not to go to heaven. World's End is literally a waterfall going off the 'edge of the world', and below the waterfall is kind of a desert paradise/oasis. Jack is there with a rather mutalated Black Peal. There he meets some strong and rather friendly crabs who take him and the Pearl to Elizabeth and Will and Barbossa and Tia and all them. They sailed off the end of the waterfall to get into World's End. Meanwhile Davy Jones and Norrington are on the Flying Dutchman and Davy Jones is under the control of the East India Trading Company A.K.A. Beckett who has ordered him to... let's just say "dispose" of all pirates on the seven seas. Of course, Jones isn't too thrilled with the idea but has no choice or else Beckett would stab his heart. But I've only read the first few chapters of the script, so I don't know exactly what will happen in the end, but I have heard things. I will give you some hints though that two men die in the first part of the movie. But that's all I'm saying!