Basically, the goddess of discord was unhappy that she wasn't invited to a Greek god party so she made an apple out of gold for the prettiest goddess. Three started fighting claiming that they were the prettiest and decided to let a man, Paris, decide who was the prettiest. When they tried to bribe him, Aphrodite offered to give him Helen of Sparta as a wife. He accepted and since he was from Troy and she was the wife of King Menelaus, war began between Troy and Greece, known as the Troyan War.
