Mantra is a set of particular words in a particular configuration and rhythm by chanting which one can fulfil one's wish.
Tantra means a method to perform a worship in a systemised way.
Yantra is a geometric figure inscribed on a metallic plate or paper and is the confluence of the powers of the concerned God.
When a Mantra is chanted according to the proper Tantra, the sound vibrations gather force from the Yantra and after reflecting from its surface spread out into the universe and reach the concerned God. These vibrations come into contact with the form of the God, gather divine powers and blessings from Him and return to the Sadhak (person chanting), thus instilling divinity into him and giving him power to achieve supernatural feats.Thus, to achieve totality of life three ingredients Mantra, Tantra and Yantra are essential because all three are supplements of each other. This is the Science.Vigyan means science in Hindi Language.
The aim of life is to keep rising high, to achieve great heights and to keep attaining success. But this is easier said than done. For achieving totality i.e. Dharma(righteousness), Artha (wealth), Kaam (pleasures) and Moksha (salvation) ; and for attaining fame, respect and success in one's field of work one needs Divine assistance, which can only be obtained with the help of Mantra-Tantra and Sadhanas.
Indian knowledge had proved the mettle of its superiority long back and even in the modern scientific times its significance remains unmitigated. This rich heritage, was for selfish interests, presented in a very ugly and distorted form before the society; so much so that the words like Mantra & Tantra became synonyms of fear for the common folk. Thus due to ignorance Tantra became a tabooed and much dreaded word in society and people became petrified just by hearing about it. The common man thinks that a Tantrik is a person who drinks liquor, smokes opium, abuses everyone, has large redshot eyes, one who can kill anyone and who always remains engaged in evil works.
Nothing is further from the truth. Such people are imposters, they are not Tantriks. Tantra actually means accomplishing Mantra Sadhana in a very systemised way. If there is a Mantra then the process of its use is Tantra. Tantra is the way to perform a Sadhana(meditation) in a proper and correct manner. The method or way to achieve totality in Sadhana is Tantra.
True knowledge knows no bounds and this is especially true about Indian knowledge of Sadhanas (meditation), Yoga & philosophy, which has been illuminating the path of world peace and brotherhood since ages. In fact, these principles make it more a system of life, than mere knowledge.
The ancient Indian sages and ascetics had achieved full perfection and harmony with the nature, and they could perform seemingly impossible feats. The Ramayan, Mahabharat and other Indian texts are full of such examples, but today the so-called "rational" mind dismisses them as mere myths and superstition.
Most of the true knowledge has been lost due to foreign onslaught over the past millennium. The common man goes to a temple or ashram, sings some hymns, touches the feet of some Swami who nods his head, charges huge fees as "Dakshina" and assures positive results. Then he merely recites mugged up verses and mantras without producing the desired results. Upon failure and having become thoroughly dejected, the common man dismisses all ancient Indian spiritual sciences as hoax and swindle.Link