The sacred mantra, or the Divine Name, is a vital symbol of the Supreme Divinity, directly revealed in the innermost depths of divine communion to the sages of Self-realisation, in the hoary Vedic and Upanishadic times.
Mantra Yog is an exact science. A mantra, in the Hindu religion, has the following six parts. It has got a rishi who had Self-realisation for the first time through this mantra, and who gave this mantra to the world. Sage Vishwamitra is the rishi for Gayatri.
Second, the mantra has a metre that governs the inflection of the voice. Third, the mantra has a particular devata as its informing power. This devata is the presiding deity of the mantra. Fourth, the mantra has got a bija, seed. The seed is a significant word, or series of words, which gives a special power to the mantra. The bija is the essence of the mantra.
Fifth, every mantra has got a shakti, the energy of the form of the mantra. Lastly, the mantra has a kilaka – pillar, pin. This plugs the Mantra Chaitanya hidden in the mantra. As soon as the plug is removed by constant and prolonged repetition of the Name, the chaitanya that is hidden is revealed. The devotee gets darshan of the Ishta Devata.