Paris is deciding between Hera, Athena, and Aphrodite on who should get the golden apple.
Hera is on the far left and is the queen of all gods and is offering Paris the ruler of the world . Athena is in the middle and he is the goddess of wisdom and war and is offering Paris victory in all wars. Aphrodite is on the far right and is the goddess of love and beauty and is offering Paris the most beautiful woman in the world as his wife.
Paris chose Aphrodite and Aphrodite took Paris to the palace of Menelaus at Sparta to meet Helen(wife of the Greek king Menelaus).
Paris seduced the the queen and abducted her back to Troy and that made the Greeks mad.
The theft of Helen was an act of of outrage which invoked the oath of Tyndareus, requiring the untied powers of the Greeks to avenge the wounded honor of Menelaus and retrieve Helen.
Odysseus had a great idea of building a large wooden horse and would hide the Greek warriors inside of it. They left the Horse outside the gate as a present and pretended to sail away. That night Trojans took the horse inside the city. The warriors crept out and threw open the the city's gates . The Greeks entered and sacked the city to claim a victorious end to the Trojan war.