Image from WoW-Wiki
You've seen monuments dedicated to her. You've heard her name praised by night elves all across Azeroth. Her name is on weapons, robes, and even songs on the WoW soundtrack.
So who is the mysterious Elune?
Elune has been called "one of Azeroth's few full deities," and can be referred to by several names. Mother Moon and the Night Warrior are names common to members of the Alliance, and the tauren have given her the name Mu'sha, the left eye of the Earthmother.
She has many followers, beginning with the religious order "The Sisters of Elune." As the name implies, it is composed of women who have been endowed with magical powers by the goddess herself. They can heal an ally near death or curse an enemy on the battlefield. The sect is led by High Priestess Tyrande Whisperwind, and is the highest order of Elune's priests.
According to the World of Warcraft website, all the priests who served Elune were originally night elf women. Gradually over time the order has allowed both men and a few priests of other races to join. However, they believe that Elune's magnificence can only truly be understood by women, and so the Sisters of Elune are still excusively female.
She is often depicted as a beautiful night elf woman crowned with a simple platinum circlet and surrounded by dazzling luminescence. Artists also traditionally portay her with long, white hair, alabaster skin, and eyes of pure moonlight. - WoW.com
Elune is also known for the creation of the moonkin, whose purpose was to protect areas she deemed sacred, including her shrines.
She had a romantic relationship with the forest demi-god Malorne, and that union led to the birth of the famous Cenarius.
Very little is known about Elune, as she has never been seen in a physical form by any mortal, and some even believe her to be a "collection of ideals" rather than an actual physical presence. Whatever the case may be, she has had a profound impact on both night elf and tauren cultures, and her priestesses still keep watch over her temples.