Call To Tara, Goddess of Compassion...

Praises to the 21 forms of Tara...

Green Tara: 

OM represents Tara's sacred body, speech and mind.
TARE means liberating from all discontent.
TUTTARE means liberating from the eight fears, the external dangers, but mainly from the internal dangers, the delusions.
TURE means liberating from duality; it shows the true cessation of confusion.
SOHA means "may the meaning of the mantra take root in my mind."

Tara (whose name means "star" or "she who ferries across") is a Bodhisattva of compassion who manifests in female form. 

In Tibetan, Tara is known as "Dölma", or "She Who Saves." In particular she represents compassion in action, since she's in the process of stepping from her lotus throne in order to help sentient beings. 

Tara's mantra is a loving play on her name. According to Sangharakshita, a traditional explanation of the mantra is that the variations of her name represent three progressive stages of salvation:
1. Tāre represents salvation from mundane dangers and suffering. Tara is seem as a savioress who can give aid from material threats such as floods, crime, wild animals, and traffic accidents.

2. Tuttāre represents deliverance into the spiritual path conceived in terms of individual salvation. In traditional terms, this is the path of the Arhant, which leads to individual liberation from suffering. This is seen in Mahayana Buddhism as a kind of enlightenment in which compassion does not figure strongly.

 
3. Lastly, ture represents the culmination of the spiritual path in terms of deliverance into the altruistic path of universal salvation - the Bodhisattva path. In the Bodhisattva path we aspire for personal enlightenment, but we also connect compassionately with the sufferings of others, and strive to liberate them at the same time as we seek enlightenment ourselves.
 
Svaha, according to Monier Monier-William's Sanskrit Dictionary, means: "Hail!", "Hail to!" or "May a blessing rest on!" Her mantra can therefore be rendered as something like "OM! Hail to Tara (in her three roles as a savioress)!" although this may one of those occasions when the mantra is best left untranslated.

White Tara:  

The mantra for White Tara is:
OM. TARE TUTARE TURE. MAMA AYUR PUNYE JNANA PUSHTIM KURU, SWAHA

Tibetans say: OM TARE TUTTARE TURE, MAMA AYUR JANA PUNTIN KURU SOHA

White Tara is distinguished by "her body ... white, as an autumn moon; clear as a stainless crystal gem, radiating light." She has one face, two hands, three eyes. She is described in manuals as having "the youth of 16 years" but is often depicted as more full-bodied than Green Tara. Her right hand makes the gift-bestowing gesture, and with the thumb and ring finger of her left hand she holds a branch of white utpala, its petals on the level of her ear.

There are three flowers in various stages of growth symbolizing the three times (past, present and future.) The first bloom that is in seed, usually on the right, stands for Buddha Kashyapa who lived in a past eon; the second in first bloom stands for the historical Buddha Shakyamuni, whose activity has brought you here today, and the bud on the left symbolizes future buddhas -- the expected one is Maitreya Buddha.

Her hair is dark blue, bound up at the back of her neck at the back with long tresses hanging down; her breasts are full; she is adorned with divers precious ornaments, her blouse is of vari-colored silk, and her robes are of red silk, the palms of her hand and the soles of her feet each have an eye, making up the seven eyes of knowledge; she sits straight and firm upon the circle of the moon, her legs crossed in the diamond posture."

This description (Beyer 379) from the beginning of her sadhana is included as characteristic of the details in texts used as a basis for tantric visualizations. In a Buddhist sadhana, the practitioner is not really worshipping a goddess since the image is his or her own self imagined as a deity.

White Tara is referred to as "Mother of all the Buddhas." This is because she embodies the motivation that is compassion. Her whiteness "Radiant as the eternal snows in all their glory" is indicative of the selflessness -- the purity -- of this compassion but especially the undifferentiated Truth of the Dharma.

Her seven eyes stand for her perception of suffering that is apparent (the two we normally have,) that is psychological/spiritual (the one in her forehead,) and that is inherent in activity (in her palms,) and in what is usually considered as progress (in her soles.)