Yantra literally means "support" and "instrument". A Yantra is a geometric design acting as a highly efficient tool for contemplation, concentration and meditation. Yantras carry spiritual significance : there is a specific meaning that pertains to higher levels of consciousness.
The Yantra provides a focal point that is a window into the absolute. When the mind is concentrated on a single, simple object (in this case a Yantra), the mental chatter ceases. Eventually, the object is dropped when the mind can remain empty and silent without help. In the most advanced phases, it is possible to attain union with God by the geometric visualization of a Yantra. The Yantra is like a microcosmic picture of the Macrocosm. It is a focusing point and an outer and inner doorway. The Yantras are often focused on a specific deity and so by tuning into the different Yantra you can tap into certain deities or creative force centers in the universe. Yantra are usually designed so that the eye is carried into the center, and very often they are symmetrical. They can be drawn on paper, wood, metal, or earth, or they can be three-dimensional. The most celebrated Yantra in India is the Sri Yantra, the Yantra of Tripura Sundari. It is a symbol of the entire cosmos that serves to remind the practitioner of the nondifference between subject and object. How do Yantras work ?
At the basis of Yantra operation is something called "shape energy" or "form energy". The idea is that every shape emits a very specific frequency and energy pattern. Examples of old believes in shape energy are the Yantras and mandalas of eastern philosophies, the star of David, the five pointed star (pentagon), the Christian cross, the pyramids and so on. Certain 'powers' are ascribed to the various shapes. Some have 'evil' or negative energies and some 'good' or positive energies, but in Yantra Yoga only the benefic and harmonious energies are used. When one focuses on a Yantra, his mind is atomatically "tuned in" by Resonance into the specific form energy of that Yantra. The process of Resonance is then maintained and amplified. The Yantra acts only as a "tune in" mechanism or a doorway. The subtle energy does not come from the Yantra itself, but from the Macrocosm. Basically Yantra are secret keys for establishing Resonance with the benefic energies of the Macrocosm. Very often the Yantras can put us in contact with extremely elevated energies and entities, being of invaluable help on the spiritual path. Yantras are poorly known in the Occident
At this moment, there is little known about Yantras in the Western world. Many people consider them just pretty pictures and some artists claim to draw "Yantra" from their imagination. They are very far from the true meaning and use of Yantra. First of all, Yantras cannot simply be invented from imagination. Every specific mood and emotion has an associated form energy and shape. This unequivocally determines the form of the Yantra associated to that mood. The traditional Yantras were discovered through revelation, by clairvoyance, not invented. One needs to be a true spiritual master, a tantric guru, to be able to reveal a new Yantra to the world. Search the Internet and the libraries and you will find very little consistent knowledge about Yantras. Some people place Yantras upside down, a monument of their ignorance. You cannot place a Yantra just any way you please. Anyone knows that when the cross is held upside down, it is no longer a benefic symbol. A Yantra put upside down is no longer the same Yantra.
Source: magick-keys.blogspot.com