In the movie Pirates of the Caribbean 2 Dead Man's Chest, what IS the chest, & what is the legend of it?

The chest contains the heart of Davy Jones. He cut it out of his chest because the heartache of losing his true live was too much to bare. Davy jones is the captain of the flying dutchman. The only way to kill davy jones is to stab the heart. Whoever stabs the heart must replace it with his own because the flying dutchman must always have a captain.... Or somethin like that