According to the philosophy of Tantra, the entire universe is a manifestation of pure consciousness. In manifesting the universe, this pure consciousness seems to become divided into two poles or aspects, neither of which can exist without the other. Each requires the other in order to manifest its total nature.
One aspect, Shiva, is masculine, retains a static quality and remains identified with unmanifested consciousness. Shiva has the power to be but not the power to become or change.
The other aspect, Shakti, is feminine, dynamic, energetic and creative. Shakti is the Great Mother of the universe, for it is from her that all form is born.
According to Tantra, the human being is a miniature universe. All that is found in the cosmos can be found within each individual, and the same principles that apply to the universe apply in the case of the individual being.
In human beings, Shakti, the feminine aspect is called Kundalini. This potential energy is said to rest at the base of the spinal cord. The object of the Tantric practice of Kundalini-yoga is to awaken this cosmic energy and make it ascend through the psychic centers, the chakras, that lie along the axis of the spine as consciousness potentials. She will then unite above the crown of the head with Shiva the pure consciousness. This union is the aim of Kundalini-yoga: a resolution of duality into unity again, a fusion with the Absolute. By this union the adept attains liberation while living which is considered in Indian life to be the highest experience: an union of the individual with the universe. Once Kundalini Shakti has ascended to above the crown of the head and merged with Shiva, it is made to reverse its course and return to rest at the base of the spine.
In Tantrism the state of ultimate bliss is a transcendence of dualities male-female, energy-consciousness, Shiva-Shakti...