Yantra is mystical diagrams, drawn from tantric traditions of India. Tantra is a different stream based on extensive meditation and concentration to rise up the mystic power of the world. Lord Shiva is known as the lord of tantra. In tantra, the worship is done with the help of yantra. These yantras are used to please the diety. These yantras are used to worship in temples as well as at home. It can be correlated with occult power, but I can announce it to be a myth, that yantra deals with black powers. Yantra is just the mystic diagrams used to worship the lord and it was propagated by Lord Shiva, Shiva the complete GOD (generator operator and destroyer) in himself, He is believed to be the only real power source of the entire universe, for the betterment of this universe and all the existing universe. Yantra can be considered as a source of generating power of Shiva the shakti in the universe as the only hidden power through which the world is running and appears as it is in alive form.
The yantra is of a different pattern for different diety and specific for specific deities. The yantra is practiced in India from near about 11 to 10 thousand years. Or can be said from the time of Satyug when Lord Shiva was married to Parvati. Lord Shiva was the first tutor of tantra and the use of Yantra and Goddess Parvati was his first student. He taught tantra to Goddess Parvati to introduce herself with her own power, to enlighten her with the light of Addi Shakti. And then from goddess Parvati to the entire universe.
The yantra emanates from a point known as its central point or the bindu. Yantra has different shapes, different geometrical shapes, these shapes are concentric to their center, they include triangle, circle, hexagon lotus symbol, and octagon shape. These shapes include a square with four cardinal directions, each having doors on all the sides. Sri Chakra is of the same pattern and used to worship Maa Tripura Sundari. Sri Chakra is also used to please Lord Shiva, it is associated with the universe, the cosmos, and the creation. It is believed that the whole world was produced or generate by the combined performance of Lass by Lord Shiva and Maa Parvati or Aadi shakti in the origin of the universe.
These yantras are found on horizontal direction of flat surface and on a 3d tricone or triangle. They can be made by simply pasting on paper, metal or flat surface. These yantras have a similar size as that of the mandala with fewer colors as compared to mandals.
Kuber yantra it is to please Lord Kuber, for dhan labh, can be placed at house and office.
Lakshmi Yantra is for Maa Laxmi, similar in size and shape as or Sri Yantra, this yantra can be placed in the house for prosperity and to shake off poverty.
Mahamrityunjay yantra is for Lord Shiva can be placed in pooja ghar in the home for better health and to cut akkal mrityu jog.
Saraswati yantra is for Maa Saraswati can be worshiped by students to increase concentration and gain memory.
Navgrah Yantra is dedicated to the nine planets of our solar family. And can be worshiped to ward off the unpleasant or unfavorable influence of these planets and to magnify their positive effect.
Vyapar vriddhi yantra is to increase sale in the business it can be placed in office or shop.
Ganesh Yantra is for Lord Ganesha used to bring prosperity, happiness, serenity and rishi siddhi in the home.
There are specified yantra for different stars or grah and used to worship during the mahadasha of that specific star.