http://en.wikipedia.org/wiki/Mantra explains Mantra in Indo-Tibetan Buddhism
Mantrayana (Sanskrit), that may be rendered as "way of mantra", was the original self-identifying name of those that have come to be determined 'Nyingmapa'.[citation needed] The Nyingmapa which may be rendered as "those of the ancient way", a name constructed due to the genesis of the Sarma "fresh", "new" traditions. Mantrayana has developed into a synonym of Vajrayana.
Noted translator of Buddhist texts Edward Conze (1904–1979) distinguishes three periods in the Buddhist use of mantra.
Initially, according to Conze, like their fellow Indians, Buddhists used mantra as protective spells to ward off malign influences. Despite a Vinaya rule which forbids monks engaging in the Brahminical practice of chanting mantras for material gain, there are a number of protective for a group of ascetic monks. However, even at this early stage, there is perhaps something more than animistic magic at work. Particularly in the case of the Ratana Sutta the efficacy of the verses seems to be related to the concept of "truth". Each verse of the sutta ends with "by the virtue of this truth may there be happiness".
Conze notes that later mantras were used more to guard the spiritual life of the chanter, and sections on mantras began to be included in some Mahayana sutras such as the White Lotus Sutra, and the Lankavatara Sutra. The scope of protection also changed in this time. In the Sutra of Golden Light the Four Great Kings promise to exercise sovereignty over the different classes of demigods, to protect the whole of Jambudvipa (the India sub continent), to protect monks who proclaim the sutra, and to protect kings who patronise the monks who proclaim the sutra. The apotheosis of this type of approach is the Nichiren school of Buddhism that was founded in 13th century Japan, and which distilled many previously complex Buddhist practices down to the veneration of the Lotus Sutra through recitation of the daimoku: "Nam myoho renge kyo" which translates as "Homage to the Lotus Sutra".
The third period began, according to Conze, in about the 7th century, to take centre stage and become a vehicle for salvation in their own right. Tantra started to gain momentum in the 6th and 7th century, with specifically Buddhist forms appearing as early as 300CE. Mantrayana was an early name for the what is now more commonly known as Vajrayana, which gives us a hint as to the place of mantra in Indo-Tibetan Buddhism. The aim of Vajrayana practice is to give the practitioner a direct experience of reality, of things as they really are. Mantras function as symbols of that reality, and different mantras are different aspects of that reality – for example wisdom or compassion. Mantras are often associated with a particular deity, one famous exception being the Prajnaparamita mantra associated with the Heart Sutra. One of the key Vajrayana strategies for bringing about a direct experience of reality is to engage the entire psycho-physical organism in the practices. In one Buddhist analysis the person consists of 'body, speech and mind' (refer: Three Vajra). So a typical sadhana or meditation practice might include mudras, or symbolic hand gestures; the recitations of mantras; as well as the visualisation of celestial beings and visualising the letters of the mantra which is being recited. Clearly here mantra is associated with speech. The meditator may visualise the letters in front of themselves, or within their body. They may be pronounced out loud, or internally in the mind only.
[edit]Om mani padme hum
Main article: Om mani padme hum
Probably the most famous mantra of Buddhism is Om mani padme hum, the six syllable mantra of the Bodhisattva of compassion Avalokite?vara (Tibetan: Chenrezig, Chinese: Guanyin). This mantra is particularly associated with the four-armed Shadakshari form of Avalokite?vara. The Dalai Lama is said to be an incarnation of Avalokiteshvara, and so the mantra is especially revered by his devotees.
The book Foundations of Tibetan Mysticism by Lama Anagarika Govinda, gives a classic example of how such a mantra can contain many levels of symbolic meaning.
Donald Lopez gives a good discussion of this mantra and its various interpretations in his book Prisoners of Shangri-LA: Tibetan Buddhism and the West. Lopez is an authoritative writer and challenges the stereotypical analysis of the mantra as meaning "The Jewel in the Lotus", an interpretation that is not supported by either a linguistic analysis, nor by Tibetan tradition, and is symptomatic of the Western Orientalist approach to the 'exotic' East. He suggests that Manipadma is actually the name of a bodhisattva, a form of Avalokiteshvara who has many other names in any case including Padmapani or lotus flower in hand. The Brahminical insistence on absolutely correct pronunciation of Sanskrit broke down as Buddhism was exported to other countries where the inhabitants found it impossible to reproduce the sounds. So in Tibet, for instance, where this mantra is on the lips of many Tibetans all their waking hours, the mantra is pronounced Om mani peme hum.
[edit]Some other mantras in Tibetan Buddhism
The following list of mantras is from Kailash - Journal of Himalayan Studies, Volume 1, Number 2, 1973. (pp. 168–169) (augmented by other contributors). It also includes renderings of Om mani padme hum.
Please note that the word swaha is sometimes shown as svaha, and is usually pronounced as 'so-ha' by Tibetans. Spellings tend to vary in the transliterations to English, for example, hum and hung are generally the same word. The mantras used in Tibetan Buddhist practice are in Sanskrit, to preserve the original mantras. Visualizations and other practices are usually done in the Tibetan language.
Om wagishwari hum This is the mantra of the Mahabodhisattva Manjusri, Tibetan: Jampelyang (Wylie "'jam dpal dbyangs")... The Buddha in his wisdom aspect.
Om mani padme hum The mantra of Avalokitesvara, Mahabodhisattva, the Buddha in his compassion aspect.
Om vajrapani hum The mantra of the Buddha as Protector of the Secret Teachings. i.e.: as the Mahabodhisattva Channa Dorje (Vajrapani).
Om vajrasattva hum The short mantra for Vajrasattva, there is also a full 100-syllable mantra for Vajrasattva.
Om ah hum vajra guru padma siddhi hum The mantra of the Vajraguru Guru Padma Sambhava who established Mahayana Buddhism and Tantra in Tibet.
Om tare tuttare ture mama ayurjnana punye pushting svaha The mantra of Dölkar or White Tara, the emanation of Arya Tara [Chittamani Tara]
Om Tare Tutare Ture Soha.
Om tare tuttare ture svaha, mantra of Green Arya Tara - Jetsun Dolma or Tara, the Mother of the Buddhas: om represents Tara's sacred body, speech, and mind. Tare means liberating from all discontent. Tutare 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."
According to Tibetan Buddhism, this mantra (Om tare tutare ture soha) can not only eliminate disease, troubles, disasters, and karma, but will also bring believers blessings, longer life, and even the wisdom to transcend one's circle of reincarnation. Tara representing long life and health.
Om amarani jiwantiye svaha The mantra of the Buddha of limitless life: the Buddha Amitayus (Tibetan Tsépagmed) in celestial form.
Om dhrung svaha The purification mantra of the mother Namgyalma.
Om ami dhewa hri The mantra of the Buddha Amitabha (Hopagmed) of the Western Pureland, his skin the colour of the setting sun.
Om ami dewa hri The mantra of Amitabha (Ompagme in Tibetan).
Om ah ra pa ca na dhih The mantra of the "sweet-voiced one", Jampelyang (Wylie "'jam dpal dbyangs") or Manjusri, the Bodhisattva of wisdom.
Om muni muni maha muniye sakyamuni swaha The mantra of Buddha Sakyamuni, the historical Buddha
Om gate gate paragate parasamgate bodhi svaha The mantra of the Heart of the Perfection of Wisdom Sutra (Heart Sutra)
Namo bhagavate Bhaishajya-guru vaidurya-praba-rajaya tathagataya arhate samyak-sambuddhaya tadyata *Tadyata OM bhaishajye bhaishajye maha bhaishajya raja-samudgate svaha The mantra of the 'Medicine Buddha', from Chinese translations of the Master of Healing Sutra.