Mantra has been an integral part of yoga from the beginning. The utterance of these sacred sounds is said it have invoked all of the things within creation. Sanskrit when sung creates a vibrational effect that physically resonates within your body. To chant a mantra is more the just saying and affirmation (which are effective in there own way), but rather it vibrates at the frequency of creation allowing us to resonate with the what we desire.
The most powerful of all mantras are moksha mantras. These mantra are attuned to bringing the practitioner to the state of Enlightenment. Moksha mantras have been used by masters in the past known to have obtained enlightened state through the use of the mantra and have then passed it on to others.
The practice of using mantra for meditation is known as Japa yoga. This practice is considered to be the easiest for obtaining higher consciousness during this current age know as the kali yuga. Kali yuga is the iron age when humans become more materialistic and less spiritually inclined, by using japa we can focus the mind on spiritual aims and guide our minds towards transcendence.
Wikipedia defines mantra as
“A “Mantra” (/ˈmæntrə, ˈmɑːn–, ˈmʌn–/ (Sanskrit: मंत्र);) is a sacred utterance, a numinous sound, a syllable, word or phonemes, or group of words in Sanskrit believed by practitioners to have psychological and spiritual powers. A mantra may or may not have syntactic structure or literal meaning.
The earliest mantras were composed in Vedic Sanskrit by Hindus in India, and are at least 3000 years old. Mantras now exist in various schools of Hinduism, Buddhism, Jainism and Sikhism. In Japanese Shingon tradition, the word Shingon means mantra. Similar hymns, chants, compositions and concepts are found in Zoroastrianism, Taoism, Christianity, and elsewhere.
The use, structure, function, importance, and types of mantras vary according to the school and philosophy of Hinduism and of Buddhism. Mantras serve a central role in tantra. In this school, mantras are considered to be a sacred formula and a deeply personal ritual, effective only after initiation. In other schools of Hinduism, Buddhism, Jainism or Sikhism, initiation is not a requirement.
Mantras come in many forms, including ṛc (verses from the Rigveda for example) and sāman (musical chants from the Sāmaveda for example). They are typically melodic, mathematically structured meters, believed to be resonant with numinous qualities. At its simplest, the word ॐ (Aum, Om) serves as a mantra. In more sophisticated forms, mantras are melodic phrases with spiritual interpretations such as a human longing for truth, reality, light, immortality, peace, love, knowledge, and action. Some mantras have no literal meaning, yet are musically uplifting and spiritually meaningful.“