Simply stated, a mantra is a religious utterance composed in Sanskrit verse and taken from the some part of the Vedas. Mantras are articulated sounds that approximate the unsounded sound, the vibration of the Infinite that throbs in the silence of pure Consciousness.
Understand that the mantras have no literal translations. They are not words used for communication to other people. It is a language used to communicate with the divine. Mantras are vibratory tools of specific sounds which enlightened rishis and yogis heard when in deep meditative states. A mantra is composed in a special way to effect a certain result.
The Shiva Sutras tell us that the words of a mantra are only its shell, a kind of jacket. The real essence of a mantra is the subtle energy embedded in its syllables.
Mantras are the sonic bodies of the deities.
– Mark Dyczkowski
There can be a specific mantra addressed to a deity, which when chanted properly, is thought to evoke the energies of that deity. It is the most powerful form of deity energy, because it connects to the essential vibratory energy at the heart of the deity-form. Certain mantras, however, are said to hold within them the light of the formless reality beyond all forms. Om is one of those, as is Om Namah Shivaya. That’s why the practice of these mantras can offer such a direct and immediate experience of the sacred.
If you want the truth, I’ll tell you the truth: Listen to the secret sound, the real sound, which is inside you. The one no one talks of speaks the secret sound to himself, and he is the one who has made it all.
Mantras also have a use in meditation to help achieve a certain state of consciousness.
One understanding for the word mantra is man+tra. Man means the mind (from manas) and tra means “to cross,” so a mantra is an utterance that ‘crosses the mind.” In meditation the mind is “crossed over” or silenced.
Examples such as the Gayatri mantra and Hare Krishna mantra are often chanted over and over again in a process called japa. This repetition is called mantra-japa and a devotee many take a vow to repeat a certain mantra many times a day (usually 108 times). Often during initiation (diksha) a teacher (guru) will give a special mantra to a disciple and ask him to chant it a certain number of times a day on a set of beads called a japa-mala, similar to a rosary.
The mantra recitation (japa), fire sacrifice (homa), worship (arcana), etc., must be done [in such a way, so that its performance] is balanced/harmonized with the breath (prana).
When you do mantra-japa you should do it with the feeling that you, the mantra, and the goal of the mantra are not different.