Literally, Yantra means tool or support. A Yantra is a geometric design acting as a tool for contemplation meditation and focus.
Yantra is a point source, a window into the Absolute.

When we focus intense, on a single object (in this case a Yantra), the mental chatter ceases giving up to the point when the mind can remain empty and silent without needing any help.

Yantra is like a microcosmic picture of macrocosm. It is a focal point and carries both inwards and outwards.

In essence, the Yantras are secret keys to establish a resonance with energies from the Macrocosm. Very often they put us in communion with extremely elevated energies and entities, being of invaluable help on the spiritual path.

The secret key to use them in meditation is the process of resonance. Resonance process is done by mental focusing on her image-yantra.

On the basis of operating with a yantra is called "shape energy" or "form energy". The idea is that every shape emits a specific frequency