Origin
Selene is the sister of Helios and Eos. When her brother ends his journey, she takes over: crowned with a crescent, she crosses the night in a silver chariot drawn by two white horses, and her soft light guides travellers.
The story
Her best known myth is that of Endymion, a shepherd of great beauty she finds asleep on Mount Latmos. Selene falls in love with him and asks Zeus that he never grow old: Endymion sleeps forever, and every night the Moon comes to gaze at him.
The Romans called her Luna. Over time, poets confused her with Artemis, the huntress, who also wears a crescent moon in her hair.
The symbol
The Moon orbits the Earth always showing the same face. Its cycle of phases lasts about 29 and a half days, and it gave rise to the first calendars, then to the month.
In astrology, the Moon stands for your emotions, your need for security and your memory. It rules Cancer. It is the fastest body in the sky: it changes sign every two and a half days, which is why it plays a central role in your barometer.