A mantra is composed of some letters of the Sanskrit alphabet, varnamala, which constitute words, shabda. These letters are not looked upon as mere letters. Each of them is endowed with the powers of various aspects of the Divine Mother. In other words, they are presided over by the companions of Shakti. Since innumerable permutations and combinations form the whole gamut of words, all the words uttered in the world are said to be originated from and infilled with that Shakti or power.
The Divine Mother is present in the words of benediction as also in vulgar words of abuse. The demonstration of this power of letters is witnessed in tantric worship. During all such ceremonial worships a rite called nyasa is performed by the worshipper. The meaning of the word nyasa in this context is ‘reinforcement’.
In the process each letter of the Sanskrit alphabet in serial order is ‘reinforced’ into a particular point in the whole body of the worshipper in order to make the gross body scintillate with the divine resplendence of those mystic letters.
According to the tantras, from the supreme Self came out Shakti, the primal energy, and from this Shakti originated the basic vibration or sound, nada, which later on compressed itself into a bindu, a nucleus of power. This bindu again burst into nada to create complete focal points termed bijas. The process by which these bijas are transmitted by the guru to the disciple is known as diksha or initiation into the spiritual path.