OM is the primordial sound, the sound of creation.
The single word OM (ॐ) is known as the primary or bij mantra because it contains the s
eed for all other mantras within itself.
That alone is the self; On which are woven the earth, intermediate region and sky, the mind, together with all its breaths. Put away all other words, for OM is the channel to the immortal Brahman.