A mantram is a combination of sounds, of words and of phrases which, through virtue of certain rhythmic effects, achieve results that would not be possible apart from them.

The potency of a mantram depends upon the point in evolution of the one who employs it. Uttered by an ordinary man it serves to stimulate the good within his bodies, to protect him, and it will also prove of beneficent influence upon his environment. Uttered by an adept or initiate its possibilities for good are infinite and far-reaching. - A Treatise on Cosmic Fire, p. 926,

A mantram, when rightly sounded forth, creates a vacuum in matter resembling a funnel. This funnel is formed betwixt the one who sounds it forth and the one who is reached by the sound. There is then formed a direct channel of communication.
- Letters on Occult Meditation, p. 164

There are mantrams for use in healing, mantrams of protection, mantrams of discipleship, mantrams that put one in touch with the Will or with the Love aspect, or with Light; mantrams that invoke the God within, that work with the matter of the mental plane abstract or concrete. There are mantrams that can only be entrusted to initiates and the Masters, dealing with relationships beyond our comprehension.

The first Aspect works through a Word of Power. The second Aspect works through Mantric combinations. The third Aspect works through mathematical formula.