According to Vajrayana Buddhism Tara is a completely enlightened Buddha who made a promise in the distant past that after reaching complete enlightenment she would always appear in the form of a female for the benefit of all beings. The most common forms of Tara are the green which is considered special for all types of activities, white for longevity, and red for power.
Practiced by all four major schools of Tibetan Buddhism, White Tara has been the main deity practice of many well-known Buddhist scholars and siddhas in both India and Tibet, foremost among whom where Nagarjuna and Atisha. White Tara’s special function is to promote long life, both for the practitioner and for others. Ultimately, she is the very nature of the dharmakaya, and her practice is a means for attaining realization and accomplishing liberation.