Om is the highest Mantra. Om helps to open the heart, to elevate the consciousness. Om activates the Chakras, especially the Ajna Chakra. Om is very famous in the Mandukya Upanishad, in the Bhagavad Gita und the Yoga Sutra.
Om can be used for meditation, for chanting, for humming. And you can hear the sound of OM in everything: The sound of the forests, the waves of the ocean, the sound of the wind – it is all OM. Even cars, motor cycles, machines, Computers – they all do OM.