Yantra literally means "Instrument". A Yantra is a geometric design acting as a highly efficient tool for contemplation, concentration and meditation. Yantras carry spiritual significance and point the user 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 object ( in this case a Yantra ), the mental distractions 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.
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 energy, but in YANTRA only the benefic and harmonious energies are used.
When one focuses on a yantra, his mind is automatically "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, yantras are described in the Vedas as secret keys for establishing RESONANCE with the beneficial energies of the MACROCOSM. Very often the yantras can put us in contact with extremely elevated energies and entities, thereby providing invaluable help on the spiritual path.