The maternal Tara is one the most widely revered within the old Indo-Tibetan Buddhist world. However, she is not as well-known within the earlier diffusion of Chinese Mahayana Buddhism. Even then, some Lamas proclaim that Kuan Yin (a popular Chinese Bodhisattva of compassion) as a manifestation of White Tara (one of the more popular forms of Tara).
Tara is Sanskrit and is loosely translated as the saviouress. She has 21 main forms which is derived from Green Tara, which incidentally is her main form and the most popular image of her. She has emerald-green skin with her left hand lightly placed at the level of her heart with her ring finger and thumb joining - a symbolic gesture of bestowing supreme refuge.
Her right hand rests downwards near her knee with her palms exposed and her thumb and index fingers joint, which means that she grants worldly and ultimate (spiritual attainments) boons. Her left leg is enclosed in the posture of medition while her right leg is uniquely outstretched. This is of powerful significance for devotees of Tara because the posture of her legs signifies her strong affinity she has with us (because she is ever ready to come to our aid).
Tara was first revealed to us by Vajrapani, one of the 8 main Bodhisattva students of the historical Buddha. She is said to be a female student of a Buddha of another place and time. Her refusal to accept gender discrimination and her eventual enlightenment led her to assume her female form. She is said to assume that form to protect all Beings from fear and from our their limitations imposed by gender, preferences and various other attachments.
Tara is said to be one of the most sensitive to devotees. She has manifested to innumerable Indian and Tibetan masters of the past. She manifested to Atisha, the great Indian master of old and told him to go to Tibet. Tara and Lama Tsongkhapa statues are some of the most common deities to manifest miracles. She is also very efficacious to help those who seek her assistance.
Her mantra is Om Tare Tuttare Tore Soha.