Om Mani Padme HumBeautiful, soothing to the soul, and it touches me deeply.
Tibetan Buddhists believe that saying the mantra (prayer), Om Mani Padme Hum, out loud or silently to oneself, invokes the powerful benevolent attention and blessings of Chenrezig, the embodiment of compassion. Viewing the written form of the mantra is said to have the same effect -- it is often carved into stones, like the one pictured above, and placed where people can see them.
It is said that all the teachings of the Buddha are contained in this mantra: Om Mani Padme Hum can not really be translated into a simple phrase or sentence. http://www.dharma-haven.org/tibetan/meaning-of-om-mani-padme-hung.htm