What does it mean by;
"If a face could launch a thousand ships".
"The face that launches a thousand ships".
Helen of Sparta was regarded as the most beautiful woman in Greece. She was abducted by Prince Paris and taken to Troy, which led to her husband Menelaus calling on all the kings of Greece to help him in getting her back. To do this, a thousand ships were needed to carry the armies.
So her beautiful face led to the launching of a thousand ships.
It is used to say someone is extremely beautiful.