The thing Tibetans shake is called a prayer wheel. In areas of Tibetan Buddhism, Tibetans often spin prayer wheels containing scriptures while reciting the six-character sutra oum, ma, ni, be, mei, hom. It is equivalent to chanting sutras and is a way of practice.
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Prayer wheels are also called Mani prayer wheels, Brahma prayer wheels, prayer barrels, etc. They are related to the Eight-Character Mantra and the Six-Character Mantra (Six-Character Great Ming Mantra) Tibetan Buddhism believes that the more you recite mantras, the more you show your devotion to the Buddha, and you can escape the suffering of reincarnation. Therefore, in addition to reciting orally, people also make mani prayer tubes, put the six-character Great Ming Mantra scroll in the prayer tube, and turn it by hand. The Tibetan people put the scriptures in the prayer tube, and each rotation is equivalent to Reciting the sutra once means reciting the six-character Great Ming Mantra hundreds and thousands of times.
Whether it is a hand-cranked one or a fixed one in a temple, the structure of the prayer wheel is similar. There is a sutra written in Tibetan inside. Because during the slavery era, most Tibetans were illiterate, so they put the sutras in the prayer wheel. Each turn is equivalent to reciting the sutra once. The prayer wheel has a rotating shaft, and every time it rotates to a certain number of turns, it must be updated, so that Tibetans can know the number of times they have recited the scriptures.