Symbolism, Imagery, Allegory
Poor Portia. Even though her father is dead, the guy still manages to orchestrate her marriage from the grave. In his will, Portia's father stipulated that her husband would be determined according to a lottery (yeah, we know, it's more like a contest). Since Portia is rich, smart, and beautiful, men travel from all over the world for a chance to marry the heiress.
Here's how it works. A suitor is given the option of choosing one of three caskets (see below). If he guesses correctly, he gets Portia and all her money. If he chooses incorrectly, he has to leave Belmont immediately and can never, ever marry. Apparently, Portia's dad reasoned that the man who chooses the correct casket (which holds a picture of Portia inside) will be the right man for our girl.