Om mani padme hum is the six syllable mantra of the avalokitesvara, known as a savior and protector from the dangers. It is believed that one who chant this mantra, will be saved from all dangers and the misery in the life. This mantra is widely used in mahayana buddhism for different purposes from chanting to using them in arts.
The mantras are often found inscribed on rocks, prayer wheels, chaitya walls, paths, the approaches and exists of the villages. It is said that all teachings of buddha life are contained within om mani padme hum. Shortly called as mani mantra, the mani mantra can be chanted and recited by anyone who feels like practicing it and doesnt require any buddhist master to do so.
Mani wheel found on the stupas are spun and spinning the wheels gives the same benefit as reciting the mantra. The mantra can be found on the small hand wheels or a large wheel with millions of copies of mantra inside.