The difference between Mantra, Yantra and Tantra.
Mantra means designation in the form of Sound. Supreme consciousness is designated by a sound formula.
In Tantra there is symbolism in the form of Human or Animal figures, such as the figures in human shape or in animal shape.
Yantra is a psyshic sumbol.
Aum is both mantra and Yantra, because Tantra must have a human symbol.
Aum is a mantra and every mantra has two forms : It has sound and a form, Aum has a form which is visible to the eyes and at the same time it has a sound.
So, Aum as a mantra is subject to perception and hearing.
Yantra also has the diagrams and sounds,
But Tantra has no sound. It only be seen, not heard.
In Yantra a beeja mantra is also added and thus a yantra is a combination of sound and form with a beeja mantra.
Author is student to PG department of yoga, Ranchi University.