In there most basic form, yantras are repeating patterns that enable the viewer to go into a meditative state. Yantras exist in every great spiritual tradition: Christianity, Buddhism, Islam as well as Hinduism.

Shown here is a tradtional yantra showing the shakti (yoni mudra) and shiva mudra as well as the Deva Devi Mudra (combination of both yoni and shiva mudras.symbols. The link provided here enables you to see how a traditional yantra is constructed.