The Tibetan Mani wheel (prayer wheel) is a cylindrical wheel on a spindle. It is made from metal, leather and wood. It plays a very important role in Tibetan Buddhist tradition.
The mantra ओं मणिपद्मे हूं Oṃ maṇi padme hūṃ that is on the outside of the prayer wheel is associated with the four-armed Shadakshari form of Avalokiteshvara, the bodhisattva of compassion. The mantra is especially revered by devotees of the Dalai Lama, as he is said to be an incarnation of Avalokiteshvara.
The concept of the prayer wheel is a physical manifestation of the phrase "turning the wheel of Dharma," which describes the way in which the Buddha taught. Prayer wheels are used to accumulate wisdom and merit (good karma) and to purify negativities (bad karma).
The practice of spinning the prayer wheel helps with the mind-stabilization technique that trains the mind while the body is in motion. Buddhist teachers extol its ability to quickly harmonize the environment, promote healing, increase compassion, and assist practitioners on their journeys to enlightenment.