Yantra is the Sanskrit word for "instrument" or "machine". The meaning is contextual. Much like the word 'instrument' itself, it can stand for symbols, processes, automata, machinery or anything that has structure and organization.
Be it a complicated form of vedic ritual such a yajna or some simple form of worship performed ordinarily in millions of Hindu households everyday,the process of worship in Hinduism invariably involves the use of three basic techniques, namely the mantra, the tantra and the yantra.
Symbolically, they represent the three basic spiritual paths of Hinduism, made hugely popular by the teachings of Sri Vasudeva Krishna in the famous Bhagavad gita. The mantra symbolically represents the use of Jnanamarg, the path of knowledge, the tantra of Bhaktimarg, the path of devotion, and the yantra of Karmasanyasmarg or the path of detached action. Unless these three are present in some form or combination, the worship is incomplete.
The Use of Yantra
Yantra is the use of certain external objects, symbols or some mechanical means to worship the divine. The act of folding of hands in front of the deity is but a kind of yantra only. The manner in which a fireplace is built for the performance of some vedic sacrifice, the method in which the place is prepared and the materials (sambhra) are assembled, the manner in which the oblations are poured into the fire, the way the priests sit around the altar, and in fact the very act of chanting of the mantras with mechanical precision form part of yantric worship only.
The very design of the temple as an outer symbol of the existence of the Divine on the material plane, the act of visiting the temple, circling around the temple, entering the temple, the lighting of the lamps in front of the divine, the decorations and the ornamentation so characteristic of hindu temples and places of worship, the manner in which the images are built and installed, the lighting of the lamps, the offerings, the method of worship, the partaking of prasad, and in short any practice that is mechanical, symbolic and ritualistic to a degree, form part of this approach only.
Shapes and patterns commonly employ ed in yantra include squares, triangles, circles and floral patterns but may also include more complex and detailed symbols, for instance: The lotus flower typically represent chakras, with each petal representing a psychic propensity (or vritti) associated with that chakra. A dot, or bindu, represents the starting point of creation or the infinite, unexpressed cosmos. The shatkona (Sanskrit name for a symbol identical to the star of David) composed of a balance between: An upwards triangle denoting action (or service), extroversion, masculinity or Shiva A downwards triangle denoting introversion, meditativeness, goddess energy or Shakti A swastika represents good luck, welfare, prosperity or spiritual victory Bija mantras (usually represented as characters of Devanagari that correspond to the acoustic roots of a particular chakra or vritti) The Shri Yantra is one of the most famous and ancient yantra.