Eris, goddess of discord was angry at not being invited to the royal wedding
Eris threw a golden apple at the guests to see who was the fairest of them all
Hera, Athena, and Aphrodite all thought they were the fairest.
Zeus would not settle the dispute so he had Paris settle it.
Paris was raised as a Shepard because it was prophesied that he would cause the down fall of troy.
For the apple, Hera told Paris she would make him the king of Europe and Asia, Athena offered to lead Troy to victory against the Greek, and Aphrodite promised him the most beautiful women in the world. He chose Aphrodite.