Kundalini means ‘coiled up’ and ‘Serpent Power.’
The Kundalini is primal energy in the form of a serpent coiled at the base of the spine. It usually lays dormant in unenlightened people. During an awakening, the Kundalini rises up through the Sushumna Nadi (the central, subtle channel), and eventually reaches the Sahasrara (Crown Chakra), thereby causing an intense spiritual awakening experience.
The Kundalini Mudra is just one of many ways to help raise your Kundalini. There is an entire yoga system called Kundalini Yoga, which was introduced to the western world by Yogi Bhajan.
Before attempting to awaken your Kundalini, your heart must be pure. If you raise your Kundalini while, for example having a deep-seeded hatred for people, it will only cause more problems.
Music: Gesticulation by Dee Vigga aka Ultra Titan:
The four fingers which encircle the index finger are symbolic of the external world, and the thumb represents the divine spirit. The left index finger represents the mind and the soul.