One of my favorite carved sculptures is of Kuan Yin in a British museum, but I only have a general understanding of the history of Buddhism and the different Bodhisattva beliefs in different countries. I have read that "In Chinese Buddhism, Guan Yin is synonymous with the Bodhisattva Avalokitesvara, the pinnacle of mercy, compassion, kindness and love" and her general wikipedia entry. I would love to hear more from a specialist.
Also interested in the variations of her origin story like: "Chiang Chih-ch'i, when he penned the work, believed that the Guan Yin we know today was actually a Buddhist princess called Miao Shan, who had a religious following on Fragrant Mountain. Despite this, however, there are many variants of the story in Chinese mythology."