The Yoni is a female sexual organ indeed as structured has a cleat i.e. the phallus of Shiva.
What is Yoni ?
This is an important aspect of the female principle which the male principle does not have. Hence, the concept of the lingam-Yoni: the lingam springing up out of the Yoni. It is for the reason that the lingam never stands alone by itself, it is always found set on a Yoni. These two are inseparable and together they represent union of oneness of the male and female energy. It is also a paradoxical symbol of both possessiveness and dynamism. Both complement each other. It is always Shiva, the lingam alone that is often venerated or invoked with the Mother Goddess completely overshadowed. In Tantra it is the Mother Goddess who is supreme, she represents the dynamic force and the Shiva is in the passive state. As a symbol of union, the lingam indeed appears to have sprung out of the Yoni.
