A yantra is a geometrical pattern made of several concentric figures (squares, circles, lotuses, triangles, point). The point (bindu) at the center of the yantra signifies unity, the origin, the principle of manifestation and emanation. A yantra is the yogic equivalent of the Buddhist mandala.
When these concentric figures are gradually growing away from its center (bindu) in stages, this is for human beings a symbol of the process of macrocosmic evolution.
When they are gradually growing towards its center, this is for human beings a symbol of the process of microcosmic involution.
According to Tantra, the creation of the world begins with an act of division of the opposites that are united in the deity. From their splitting arises, in an explosion of energy, the multiplicity of the world. Starting from pure unity (Shiva), the world is a continuous unfolding (energized by the power of Shakti), until a state is reached, when the process must reverse and involute back to the very beginning. Multiplicity must once again become unity. Yantras are symbolic representations of this process of evolution and involution.
According to Tantra, the human being is a miniature universe. All that is found in the cosmos can be found within each individual, and the same principles that apply to the universe apply in the case of the individual being. For human beings the body is considered the most perfect and powerful of all yantras and is seen as a tool for inner awareness.
A yantra is thus a tool making the process of evolution conscious to the adept of Tantrism. It enables the adept to retrace his steps from the outward-directed world of multiplicity to the inward focus of unity.
All primal shapes of a yantra are psychological symbols corresponding to inner states of human consciousness. Yantras are sacred symbols of the process of involution and evolution.