Om is said to be the essence of all mantras, the highest of all mantras,
the Divine Word or Shabda Brahman itself. Om is said to be the essence of the Vedas. One need
not know or study the Vedas, one need only chant Om. Om is the sound of the infinite. It gives power
to all mantras. Hence all mantras begin and end with Om and without it
are said to be deprived of power. Om itself clears the mind for meditation.
Om consists of three sounds; the vowel 'a', the vowel 'u' and the nasalized 'm' sound. Hence it is
sometimes written as Aum (or as Alm at the beginning of the Koran, as Arabic 'l' is often pronounced as
'u' when it comes before another consonant).
The three portions of Aum relate to the states of waking, dream and
deep sleep and to the three gunas of rajas, sattva and tamas. They are
ruled by the Gods Brahma, Vishnu and Shiva, the Divine in its threefold
role as the creator, sustainer and destroyer of the universe.