Om Mani Padme Hum is the six syllabled mantra, that is particularly associated with Avalokiteshvara (Tibetan Chenrezig, Chinese Guanyin), the bodhisattva of compassion. Mani means “the jewel” and Padma means “the lotus”.
“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” symbolizes the practitioner’s impure body, speech, and mind; it also symbolizes the pure exalted body, speech, and mind of a Buddha. The path is indicated by the next four syllables. “Mani”, meaning jewel, symbolizes the factors of method: the altruistic intention to become enlightened, compassion, and love. The two syllables, “padme”, meaning lotus, symbolize wisdom. Purity must be achieved by an indivisible unity of method and wisdom, symbolized by the final syllable “hum”, which indicates indivisibility. Thus the six syllables, “om mani padme hum”, mean that in dependence on the practice of a path which is an indivisible union of method and wisdom, you can transform your impure body, speech, and mind into the pure exalted body, speech, and mind of a Buddha”. (H.H. Tenzin Gyatso, XIV Dalai lama)