In beginning there was the un-manifest Absolute. In this stillness, Consciousness stirred of its own accord and a sound arose – Om. Its vibrations rippled outwards creating Space and Time and the Universe was born.

Om is the primordial sound. It is Nada Brahman, Consciousness manifested as sound. Everything, the Vedas say, begins from Om and comes to rest in Om.

The Mandukya Upanishad begins with this beautiful declaration-

Om ityetadaksharam idam sarvam, tasyopavyakhyanam bhutam bhavat bhavishyaditi sarvam omkara eva.

OM is this imperishable Word. OM is the Universe.
The past, the present and the future, all that was, all that is, all that will be, is OM.
Likewise all else that may exist beyond the bounds of Time, that too is OM.

It goes on to say of Om,

This is the Almighty, this is the Omniscient, this is the Inner Soul, this is the Womb of the Universe.
This is the Birth and Destruction of creatures.

Om is the nama(name) rupa(form) of the Absolute. It is pranava, the source, the very breath of all mantras. It is the beej mantra, the seed that lies within all mantras.

Om is both the Self and the way to know the Self. Hence the yogis meditate upon it,focussing on its three syllables AUM .

The letter A symbolizes the conscious or waking state, the letter U is the dream state and the letter M the dreamless sleep state of the mind and spirit.

The entire symbol, together with the crescent and the dot, stands for the fourth state which combines all these states and transcends them. This is the state of samadhi or superconsciouness

This most important of Hindu symbols also forms an integral part of every Hindu’s life. All prayers begin with Om. You will find the symbol in every home and temple. All auspicious ceremonies begin with Om.  Even a newborn is welcomed into this world by an Om drawn  on his tongue with honey!  OM.