This is a picture of a tile from a temple’s wall in Kashi, the oldest part of Varanasi (Benaras) where ॐ (Om) is written in Devanagari.
Om, often Aum, is a mystical and sacred syllable in the Dharmic religions, Hinduism, Sikhism, Buddhism, and Jainism.
It is the symbol of the Absolute.
Om is reputed to be the resonant vibrational tone of the non-dualistic universe as a whole.
In Buddhism, Om corresponds to the crown chakra and white light.
Om is known in Sanskrit as praṇava प्रणव, "to sound out loudly" or oṃkāra ओंकार. "oṃ syllable".
Aum is placed at the beginning of most Hindu texts as a sacred exclamation to be uttered at the beginning and end of a reading of the Vedas or previously to any prayer or mantra.
The Mandukya Upanishad is entirely devoted to the explanation of the syllable.
The syllable is taken to consist of three phonemes, a, u and m, variously symbolizing the Three Vedas or the Hindu Trimurti or three stages in life ( birth, life and death )
The name omkara is taken as a name of God in the Hindu revivalist Arya Samaj.
Similarly, the concept of om, called onkar in Punjabi, is found in Sikh theology as a symbol of God.
It invariably emphasizes God's singularity, expressed as Ek Onkar ("One Omkara" or "The Aum is One"), stating that the multiplicity of existence symbolized in the aum syllable is really founded in a singular God.
Aum is said to be the primordial sound that was present at the creation of the universe.
It is said to be the original sound that contains all other sounds, all words, all languages and all mantras.