What is Mantra, how to use a mantra

mananat trayate iti mantraha

mantra is a sound which frees the mind from its own obsessive-compulsive thinking.

it is a science, not a knowledge or belief.

therefore, like any science, it has to be rightly learned and applied.

Gayatri Mantra best version
Learn about Sacred Sound and Mantra
The historical derivation of the science of mantra corresponds with the intricacies of the Sanskrit language - a divine language called also "mother of tongues." It is not coincidence, that the Sanskrit language is a tool for working with the subtle energy potential, represented by each chakra in the subtle body.
The word literally means "to free from the mind". So mantra is a tool used by the mind that eventually frees one from the erratic fluctuations of the mind and material inclinations. The beauty is that, in the case of mantra, its power is tangible and it can be learnt with the right guidance, patience and the right attitude.
Mantra is a sound, a sound which is related to a certain energy or form - therefore great emphasis is put on correct pronunciation, resulting in an early development of a science of phonetics in India.
The vibrations and sounds of the mantra can awaken the prana or spiritual life force and even stimulate chakras.
Chanting is the process of repeating (not singing) a mantra.