Eris(the godess of arguing) was not invited to the wedding and she decided to cause the 3 most beautiful goddesses to fight over who was the fairest of them all. They fought and fought until they decided to go to Paris the most handsome prince and ask him to choose one of them to take the apple.
Paris could not choose between the 3 amazing women, until the goddess of love promised him the heart of whatever woman he desired. Paris choose this goddesses to receive the apple and he decided the woman he wanted. A woman named Hellen, the wife of king Menelaus king of Greece.
When Paris arrived at the castle of King Menelaus he waited for the king to step away and he asked the queen if she would run away with him to Troy and become his princess. The queen quickly agreed because the goddesses of love wished it to be so. That night they sailed away leaving the king to find her missing in the morning. This infuriated the king leaving him wanting war.
They went to war! Both sides fought, and fought, and fought. This lasted for over 10 years, and millions died fighting.
The Greeks were tired of endless fighting and came up with a plan. They created a huge wooden horse, that they presented to the Trojans as a surprise. They did not know the Greeks would be inside, waiting to attack. They assumed it was a gift to the gods, that they took into their city walls.
After the Trojans brought the horse into their city, they started to celebrate. The partied for hours, until they became tired and went to bed. When they were asleep the Greeks climbed out of the wooden horse, and attacked. They fought the unprepared Trojans and claimed their victory. They burned the Trojans city and left it in ashes.