Yantra (literally “machine) is a mystical diagram, mainly from the Tantric traditions of the Indian religions. They are used for the worship of deities in temples or at home; as an aid in meditation; used for the benefits given by their supposed occult powers based on Hindu astrology and tantric texts. Yantras are usually associated with a particular deity and are used for specific benefits, such as: for meditation; protection from harmful influences; development of particular powers; attraction of wealth or success, etc. They are often used in daily ritual worship at home or in temples, and sometimes worn as a talisman.
By yantra we mean that the deity of the yantra has entered his or her power in to this geometric creation. This geometric creation is like machine which gives us enhanced output by taking input. Input means
systemic karmkand pooja + deep and intence prayer + daanam
These inputs will please the deity who in return will be pleased to shower us with his/her blessing.