Guanyin has long been my grandmother's favorite divine being. Grandma has always had a mini shrine dedicated to her on a shelf in her home. She was the one who first taught me about her in my youth.
While growing up in China, Guanyin to me was the personification of the most beautiful, the most pure, and the most gentle. I've admired many artworks of her, in her flowing white robes, with her long black hair, soulful dark eyes, and enigmatic expression, sitting or standing on her lotus seat, surrounded by her dragon companion, her young disciples, her faithful pet birds and fish, over the sea that's her home.
Guanyin is a Buddhist bodhisattva associated with mercy, kindness, compassion, and grace. She is the East Asian feminine representation of Avalokiteśvara, the principal attendant of Amitābha Buddha on the right, with 108 avatars, one notable one being Padmapāṇi (lotus bearer). Guanyin also appears in other Eastern religions as a goddess, including Chinese folk religion. She is the divine embodiment of goodness and forgiveness. The Chinese pray to her for health, fruitfulness, prosperity, and peace. She rules the seas, tames the sea monsters, controls the waves, and makes the deep waters safe crossing for fishermen and sailors. She is an eternal faithful student of Amitābha Buddha's, a teacher of his teachings, who denounces all evildoings.
Although she is most often portrayed as wearing all white, there are artworks depicting her dressed in shades of light pink, green, and blue.
Misconceptions about Guanyin in Western spiritual circles:
Guanyin is not a goddess in the same sense as the Western concept of a female deity. She is not the same as Aphrodite or Freyja, for example. According to Buddhist traditions, she is a bodhisattva (pusa in Chinese) and was once human. In Mahayana Buddhism, a bodhisattva is one who has reached immortality and divinity with bodhicitta, a sacred wish and compassionate mind to attain Buddhahood for the benefit of all sentient beings. This concept refers to a sentient being (sattva), originally mortal, who achieves enlightenment (bodhi), thus possessing the boddhisattva's divine psyche. It describes those who faithfully and diligently work to develop and exemplify loving-kindness (metta), compassion (karuṇā), empathetic joy (mudita), and equanimity (upekkha), the four divine virtues that are the "immeasurables" (brahmavihara).
She does not fit the Wiccan maiden/mother/crone triple goddess archetype at all. She is an unwed virgin. Chinese Buddhists believe in the celibacies of Buddhist divine beings. Even though she is associated with maternal qualities and motherliness, and women who wish to become mothers would pray to the "child bringer/baby sender" aspect and epithet of hers, she is not a mother herself. And she will never be a "crone".
Do not "summon" her for rituals or spell work. She is not one to be "summoned" for anything. It is incredibly disrespectful to try to do so.
She is not part of a closed practice. Buddhism is an open religion. You can worship her if you are not Buddhist or Chinese. But please do your research, and be respectful.
She is not a Pagan deity. The religions that worship her are also not Pagan religions. Please do not put her together with Paganism.
She is also not the Buddhist version of the Virgin Mary.