The Mystery of the Trojan Horse

The story of the Trojan Horse is probably one of the most famous stories ever told: after ten years of bloody war, the Greek coalition decides to lift the siege and depart, but not before leaving at the gates a huge wooden horse, which the Trojans confidently lead into the city.

A few hours later, the once invincible Troy goes up in flames. What exactly happened? Is this myth true or false?