The word "man" is translated as "mind", "tra" - "liberation". The purpose of the mantra is to lead the mind to the liberated state or, in other words, to make the mind not to be caused by external objects, which depend on the various constraints associated with time and space. But the mantra is more than just a means to achieve a transcendent consciousness, which in no way limited.
Through the mantras, we can draw some strength, which will cause certain positive changes in our ordinarily life, or at the moments of sadhana. For the right understanding of the mantras first you need to gradually learn their nature, realizing that it is not just a sound in the form as we are accustomed to perceive it. When reading the mantras we go from sound to sense, transmit audio, and then to the main essence of this meaning, reaching deep dhyana (meditation experience). Thus, sound, meaning, essence and foundation become one, and this leads to the achievement of mantra siddhi (perfection concluded in its).
The true purpose of mantras is gaining moksha, full exemption from any religious restrictions. For this purpose just one mantra is enough. In our tradition it is the mantra dedicated to Guru Gorakshanatha, Supreme Master, who is the embodiment of compassion and the giver of knowledge of the true path of yoga.
Mantras of other Deities can be read in the auspicious days, correlating with jotish (Vedic astrological calendar), and festivals like Navaratri, Shivaratri, Kalaratri.