A mantra is a sacred chant of words or sounds that are used in a spiritual practice in repetition for the purpose of transformation of consciousness and, in the case of Mahayana Buddhists, for the benefit of all beings. There are short mantras and very long complicated mantras. One of the most recognized mantras in the world is the mantra of Chenrezig, the Buddha of Compassion, which is simply, 'Om mani padme hum." (There are various spellings of this mantra, such as "Om mani peme hung" etc.)