The name Tara means to liberate all beings from the terroe of proverty and deline  and connotes being a protective mother.

In essence, Arya Tara represents the activity of all buddhas and bodhisattvas of the past, present anf future. She presents herself in the form of a goddess who indiscriminately liberates sentients beings from limiteless suffering and who therefore the supreme refuge of both samsara and nirvana.

With the respect to tara story, countless aeons ago in a world called Various light there was a tathagata name drum sound in whose teaching the princess wisdom moon had tremendous faith. she made offering to the buddha and his countless retinue of sravakas and bodhisattvas for billions of years. Each day she would lay out offerings equal in value to twelve square miles of precious jewels, covering the ten directions without empty space. It was at this time that she first gave rise to the intention to achieve supreme enlightenment.
Then the bhiksus told her, "now the roots of your virtue can ripen on this very body, turning it into that of a man. If you pray to be of service to the teachings, it shall certainly become so. you should do as such."
In response she said, "there are many who wish to achive enlightment in the form of man. there are none who benifit beings with the body of a female. Therefore, I shall serve beings in the form of a female until samsara is emptied". 
So she stayed in the kings palace for billions of years and utlizinf its luxury with skillful means, engaged in meditation. 

21 Taras are recognised as
______________________
1) swiftt and courageous Green Tara.
2)pacifying White Tara.
3)Tara whoprotects from the terror of earth.
4)Tara who protects from the terror of water.
5)Tara who protects from from the terror of fire.
6)Tara who protects from the terror of wind.
7)Enriching Tara.
8)Tara who protects from the terror of vajras.
9)Tara who protects from the terror of wepons.
10)Tara who protects from the terror of tyrants.
11)Tara who protects from the terror of thieves.
12) magnetizing Tara.
13)Tara who protects from the terror of pisacas.
14)Tara who protects from the terror of elephants.
15)Tara who protects from the terror of lions.
16)Tara who protects from the terror of snakes.
17)subjugating Tara.
18)Tara who protects from the terror of sickness.
19)Tara who protects from the terror of death.
20)Tara who protects from the terror of poverty.
21) Tara who protects from the terror of one's aims degenerating.