Ardhanarishvara is one of the 64 manifestations of Parashiva, the aspect of Lord Shiva, who is Absolute, beyond all human comprehension and is hence considered the Nirguna Brahman (the Supreme One, who is beyond attributes).
The very name Ardhanarishvara implies “the Lord who is half-woman.” Ardhanarishvara is a composite genderless form of Shiva and his consort Parvati. This form is shown as a fusion of half-male and half-female forms split down in the center. The right half is depicted as Shiva, while the left half shows the female form of Parvati.
Ardhanarishvara has an intense meaning, symbolizing the quintessential balance between the male and female energies in the universe. The forces are inseparable and complementary to each other, suggesting that they must work together to maintain the equilibrium. Since Ardhanarishvara represents the perfect synthesis of male and female forms, it also embodies the Prakriti and the Purusha, the feminine and masculine energies of the cosmos and also illustrates how Shakti, the Sacred Feminine, is inseparable from Shiva, the male principle of God.
According to our Puranic beliefs, the bones and nerves come from the father, and blood and muscles come from the mother. Due to this curse, Rishi Bhringi lost all his flesh and blood and thereby reduced him to a mere skeleton. Bhringi was all but the only skeleton now, which is believed to have come from his father, making him realize the significance of Prakriti and Purusha. He pleaded forgiveness from Parvati. Though not entirely pleased, Parvati was amazed by Bhringi’s devotion to her Lord, reconciled with Bhringi, and blessed him to have a third leg.
In another version, according to Shiva Purana, Lord Brahma, the creator of the universe, was disappointed with his creation as the world was not moving at the pace. It was constant to the number of beings he had created. There was no way out for him rather than calling Shiva for speeding the development in the world. Brahma asked Shiva for help, and Shiva took this Ardhanarishwar form to make him understand generation through copulation. Afterward, Ardhanarishwar split into Purusha and Prakriti, thus continuing the creation, suggesting that Shiva is nothing without Shakti, and creation, as well as the continuation of life, is impossible without both of them.
Ardhanarishwar is beyond our concept of gender and materializes the fact that God can be male, female, and even neuter, too. Like Ardhanarishvara, no human being is pure unisexual as each bears the potentiality of both male and female. It is the dominance of one over another that determines the sexuality of the person.