Who sings Om mani padme hum mantra? I love the tone of this song, although not understand the meaning.

Om Mani Padme Hum

https://www.youtube.com/watch?v=7FODfgCrSaw

What's her name ? Why do people venerate the bow ?
You will probably not find a better explanation than that of the Dalai Lama.

It is very good to recite the mantra OM MANI PADME HUM, but while you are doing it, you should be thinking on its meaning, for the meaning of the six syllables is great and vast. The first, OM, is composed of three pure letters, A, U, and M. These symbolize the practitioner's impure body, speech, and mind; they also symbolize the pure exalted body, speech and mind of a Buddha.
The entire talk can be found here: http://www.sacred-texts.com/bud/tib/omph.htm

Thus the six syllables, OM MANI PADME HUM, mean that in dependence on the practice which is in indivisible union of method and wisdom, you can transform your impure body, speech and mind into the pure body, speech, and mind of a Buddha. It is said that you should not seek for Buddhahood outside of yourself; the substances for the achievement of Buddhahood are within. As Maitreya says in his SUBLIME CONTINUUM OF GREAT VEHICLE (UTTARA TANTRA) all beings naturally have the Buddha nature in their own continuum. We have within us the seed of purity, the essence of a One Gone Thus (TATHAGATAGARBHA), that is to be transformed and full developed into Buddhahood. (From a lecture given by His Holiness The Dalai Lama of Tibet at the Kalmuck Mongolian Buddhist Center, New Jersey.)